The AWS Network Load Balancer (NLB) is a powerful solution designed to manage unpredictable and variable network traffic. It is built to handle millions of requests per second while maintaining ultra-low latency, making it ideal for high-performance applications that do not rely on standard HTTP traffic.
Unlike traditional load balancers that operate at the application layer, the NLB functions at the transport layer of the OSI model. This allows it to manage traffic more efficiently by routing TCP and UDP connections directly to targets. With support for TLS listeners, the NLB can even provide some functionality typically expected from application-layer load balancers.
In modern cloud-native architecture, applications often experience sudden surges in traffic. The AWS Network Load Balancer has been specifically created to respond to these challenges. It seamlessly integrates with other core AWS services such as Auto Scaling, Amazon ECS, AWS Certificate Manager, and CloudFormation. This allows for rapid deployment, automatic scaling, and flexible resource management, all of which are essential for dynamic application environments.
Core Architecture of Network Load Balancer
At its core, the AWS Network Load Balancer is composed of multiple logical components positioned between service clients and service endpoints. These components manage the distribution of packets across a fleet of registered targets. Each request from a client is matched to a specific target using advanced algorithms that ensure fairness, consistency, and high availability.
The NLB uses static IP addresses or Elastic IPs, enabling predictable inbound traffic routing. It can be deployed across multiple Availability Zones, enhancing the fault tolerance and redundancy of the system. When a target becomes unhealthy or unresponsive, the NLB automatically reroutes traffic to healthy endpoints, ensuring continuity of service without manual intervention.
The NLB is also designed to integrate deeply with Amazon EC2 Auto Scaling groups. This means it can automatically add or remove targets based on the current traffic load and predefined scaling policies. Such a mechanism enables a responsive, cost-effective solution to traffic volatility without sacrificing performance or reliability.
Operating Model and Layer 4 Functionality
The AWS Network Load Balancer operates at OSI Layer 4, which is also referred to as the transport layer. This layer is responsible for managing connection-level operations, such as TCP and UDP traffic routing. Layer 4 load balancing is efficient because it routes packets based purely on IP address and port information, avoiding the need to inspect the content of the packets themselves.
By focusing on transport layer routing, the NLB achieves extremely low latency and high throughput. This makes it suitable for real-time applications such as gaming platforms, video conferencing, VoIP systems, and financial trading systems. These use cases often demand persistent connections, fast data transfer, and high availability—all of which the NLB is designed to deliver.
Additionally, the NLB supports TLS offloading, allowing secure encrypted connections to be terminated at the load balancer level. This reduces the burden on backend servers, freeing up resources and simplifying certificate management through its integration with AWS Certificate Manager.
Handling Traffic at Scale
The Network Load Balancer can handle millions of incoming requests per second without compromising on speed or reliability. It uses a flow hashing algorithm to determine which target should handle each connection. This ensures that traffic from the same client consistently reaches the same server, which is critical for applications that maintain stateful sessions or use protocols that require connection persistence.
To scale with traffic, the NLB can dynamically distribute traffic across multiple targets in different Availability Zones. If the demand increases, Auto Scaling can add new instances, and the NLB will automatically recognize them and include them in traffic distribution. This elastic nature is a fundamental benefit of using AWS infrastructure and is crucial for businesses that experience variable traffic loads.
When there is a sudden increase in users or a major spike in traffic, the NLB continues to deliver consistent performance by balancing the connections efficiently. Unlike traditional load balancers, which might become bottlenecks under pressure, the NLB is designed to absorb and adapt to the changing conditions of modern application environments.
Security and Reliability in Traffic Management
Security is another cornerstone of the AWS Network Load Balancer design. The NLB supports the use of security groups and is fully integrated with AWS Identity and Access Management (IAM) for defining and controlling access permissions. TLS offloading at the load balancer layer also allows for more centralized security policies and certificate management.
To ensure reliability, the NLB performs regular health checks on all registered targets. If a target fails its health checks, the load balancer automatically stops routing traffic to it. This minimizes downtime and avoids service disruptions for end users.
In terms of failover, the NLB works in conjunction with Route 53 to reroute traffic if no healthy targets are available in a specific Availability Zone. Route 53 will automatically detect the unhealthy state and redirect traffic to healthy zones, providing DNS-level failover for added resilience.
Integration with AWS Ecosystem
The NLB integrates seamlessly with a wide range of AWS services. These include Auto Scaling, CloudFormation, ECS, AWS Certificate Manager, and AWS Elastic Beanstalk. This compatibility allows developers and DevOps teams to include NLB as a foundational component in their infrastructure-as-code deployments or containerized applications.
For example, in a microservices architecture using ECS, each containerized service can be registered as a target group behind the NLB. This provides each service with fault tolerance, automatic scaling, and secure communication. The load balancer can forward traffic to different ports and protocols as needed, making it highly flexible and adaptable to complex environments.
Additionally, the centralized API used by both the NLB and Application Load Balancer simplifies management tasks. Developers can use familiar tools and methods to configure, monitor, and maintain their load balancers, reducing the learning curve and operational overhead.
Use Cases and Ideal Scenarios
The AWS Network Load Balancer is ideal for scenarios where extreme performance, low latency, and high reliability are required. These scenarios include real-time multiplayer gaming, live video streaming, high-frequency trading platforms, and Internet of Things (IoT) applications. These types of workloads require persistent connections and can generate unpredictable bursts of traffic.
Another common use case is within hybrid cloud environments where on-premises infrastructure connects with cloud services. The static IP capabilities and secure TLS support make the NLB a suitable solution for bridging such environments with minimal complexity.
Enterprise applications that need fixed IP addresses, fault tolerance, and secure communication over TCP or UDP will benefit greatly from the features of AWS Network Load Balancer. It’s also a good choice for systems that require direct access to the client’s IP address, which is preserved in the packet as it is forwarded to the target.
How AWS Network Load Balancer Works
Understanding how the AWS Network Load Balancer operates internally provides better insight into its role in managing modern, high-performance applications. Unlike traditional load balancers that focus on application-level routing, NLB works at the transport layer. This allows it to process and route raw TCP and UDP connections with minimal overhead.
When a client initiates a connection, the NLB uses a flow hashing algorithm to determine which target in its target group will receive the request. The selection process is deterministic for the lifetime of the connection, meaning all packets for that session are consistently directed to the same target. This makes it suitable for applications that rely on connection persistence.
The NLB supports both IPv4 and IPv6 traffic. It accepts connections using Elastic IP addresses or DNS names, and then forwards the traffic based on the port and protocol rules defined in the listener configurations. Each listener checks for incoming connections and distributes them to healthy targets in the associated target group.
Components of AWS Network Load Balancer
Several key components work together within AWS Network Load Balancer to ensure traffic distribution is efficient, reliable, and secure.
Listeners
Listeners are defined by a port and a protocol. They listen for incoming connection requests and forward them to target groups. NLB supports TCP, UDP, and TLS protocols for listeners. When a listener receives a request, it follows the configured rules to route it to an appropriate target group.
Target Groups
A target group is a collection of servers or services that receive traffic from the load balancer. Each target can be identified by an IP address or an instance ID. Targets can be located in one or more Availability Zones to enhance redundancy and availability. Health checks are configured at the target group level, and only healthy targets will receive traffic.
Rules
NLB uses rules to determine how traffic is routed to the target groups. These rules can define conditions based on source IP addresses and ports. Although less flexible than application layer load balancers, these rules are sufficient for high-performance, connection-based workloads.
Health Checks
To ensure that only functional resources receive traffic, the NLB periodically performs health checks on all registered targets. These checks use TCP or HTTP and are configured with a path, port, timeout, and interval. If a target fails its health checks, it is temporarily removed from service until it becomes healthy again.
Availability Zones and Elastic IPs
The NLB can be configured to operate across multiple Availability Zones. Each zone can be assigned an Elastic IP address, which allows clients to connect using a static IP. This is particularly useful for applications that require IP whitelisting or integration with firewall appliances.
Traffic Distribution and Load Balancing Logic
The AWS Network Load Balancer uses a flow hash algorithm that takes into account multiple elements such as source IP address, source port, destination IP address, destination port, and protocol type. This helps ensure that packets from the same connection are consistently routed to the same target, preserving session integrity.
When a new TCP or UDP connection is initiated, the NLB selects a target from its target group using this hash. Once a connection is established, all packets associated with it are sent to the chosen target until the session ends.
The NLB does not inspect the contents of the packets. This improves efficiency and reduces latency, especially for high-throughput applications. Since there is no content inspection, the NLB is not protocol-aware and relies solely on the information at the transport layer.
Persistent Connections and Session Handling
AWS Network Load Balancer supports persistent TCP connections. These connections can remain open for extended periods, which is particularly beneficial for applications like online gaming, financial systems, and messaging platforms that require long-lived sessions.
Session persistence is handled based on the connection’s flow hash. As long as the client maintains the same source IP and port, and the destination IP and port remain unchanged, the connection persists to the same target.
The idle timeout for TCP connections is configurable, allowing developers to maintain connections as needed. This provides flexibility in tuning the load balancer to fit different application behavior patterns.
NLB with TLS Termination
The AWS Network Load Balancer supports TLS termination, which enables it to offload the TLS decryption process from backend targets. This is especially useful in cases where backend systems are not optimized for TLS or when central management of TLS certificates is needed.
TLS termination is configured through the creation of a TLS listener on the NLB. The listener references a certificate managed through AWS Certificate Manager. When a client initiates a TLS handshake, the NLB handles the encryption and decryption process, forwarding decrypted traffic to the backend servers.
The main advantage of TLS termination is reduced resource consumption on backend servers. It also centralizes certificate management, simplifies compliance, and enhances security monitoring. For organizations that need encrypted connections with minimal operational burden, this feature is highly beneficial.
NLB and High Availability Architecture
The architecture of the AWS Network Load Balancer is inherently designed for high availability. It supports deployment across multiple Availability Zones, and each zone can be associated with its own set of targets. If one zone becomes unavailable or if the targets within that zone fail health checks, the NLB reroutes traffic to healthy targets in other zones.
DNS-level failover is supported through Route 53. If an entire region or set of zones becomes unreachable, Route 53 can redirect traffic to other regions or alternative endpoints. This architecture makes the NLB a key component in building fault-tolerant applications that require continuous uptime.
The use of Elastic IPs also enhances reliability. Elastic IPs provide static addressing, which is especially valuable when clients require fixed IP addresses or when integrating with security appliances that depend on IP whitelisting.
Integration with Auto Scaling
The AWS Network Load Balancer works in perfect synergy with EC2 Auto Scaling. When Auto Scaling adds or removes instances based on load, the NLB automatically registers or deregisters those instances as targets. This dynamic integration ensures that the load balancer always reflects the current state of the application infrastructure.
This combination allows for responsive scaling based on real-time traffic patterns. When traffic increases, new instances are launched, and the NLB immediately begins routing traffic to them. When demand decreases, unused instances are terminated, and the NLB stops directing traffic to them.
This level of automation significantly reduces operational complexity and enables businesses to maintain optimal resource usage, minimizing costs while maintaining performance.
Monitoring and Logging
The AWS Network Load Balancer provides a suite of monitoring and logging capabilities through AWS CloudWatch, AWS CloudTrail, and VPC Flow Logs.
CloudWatch metrics allow administrators to track important metrics such as active connections, new connections, processed bytes, and unhealthy host counts. Alarms can be set up to notify operators of anomalies or failures.
CloudTrail records API activity related to the NLB, offering a valuable audit trail for compliance and security investigations.
VPC Flow Logs capture detailed information about traffic flowing through the NLB. These logs can be used to analyze traffic patterns, detect unauthorized access, and troubleshoot network issues.
This observability stack enables fine-grained visibility into the load balancer’s behavior and allows for proactive performance and security management.
Real-World Scenarios and Best Practices
Many enterprises use AWS Network Load Balancer for mission-critical workloads where performance and reliability cannot be compromised. Financial institutions, e-commerce platforms, streaming services, and healthcare systems are just a few examples.
For best results, it is advisable to design applications with zonal redundancy. Deploying targets across multiple Availability Zones ensures that the failure of a single zone does not result in downtime.
Another best practice is to monitor health check configurations closely. Proper health check intervals, thresholds, and timeout settings are crucial to avoid false positives and ensure timely removal of unresponsive targets.
TLS termination should be used wherever encrypted traffic is required. It centralizes certificate management and improves backend performance. When using TLS listeners, ensure certificates are rotated regularly through AWS Certificate Manager.
For organizations that require IP whitelisting or need to comply with strict security policies, using Elastic IPs provides the necessary control and consistency.
AWS Network Load Balancer Features
AWS Network Load Balancer offers a range of features tailored to support high-throughput, low-latency applications across multiple network layers. These features make NLB an ideal solution for developers and system architects working with scalable, reliable systems.
Zone-Based Isolation
The Network Load Balancer is built with zonal awareness. It can be deployed within a single Availability Zone or across multiple zones. This zonal isolation capability supports application designs that require fault isolation, where specific zones operate independently from others. If a zone becomes unavailable, other zones continue to operate without disruption, improving fault tolerance.
This design is helpful for applications with specific zone affinity or requirements for disaster recovery. For example, a legacy application running only in one zone can still leverage the high performance and availability benefits of NLB.
Permanent TCP Connections
Network Load Balancer supports long-lasting TCP connections. These connections can remain open for extended durations—ranging from hours to even months. This capability is critical for applications such as gaming servers, live financial market feeds, streaming services, and WebSocket-based chat applications.
NLB preserves the client-to-target connection, ensuring minimal interruption even during fluctuations in load or backend changes.
Centralized API Management
NLB uses a consistent API structure shared with the Application Load Balancer. This uniformity allows users to manage both load balancer types using the same tools and processes. Through this API, developers can configure listeners, define target groups, manage health checks, and implement automation via Infrastructure as Code solutions.
Having one API model simplifies system management, especially in environments where both L4 and L7 load balancers are used.
Integration with AWS Services
AWS Network Load Balancer integrates seamlessly with a broad range of AWS services. These include:
- Amazon EC2 Auto Scaling
- Amazon ECS (Elastic Container Service)
- AWS CloudFormation
- AWS CodeDeploy
- AWS Certificate Manager (ACM)
- AWS CloudTrail
- AWS Config
- AWS Elastic Beanstalk
This tight integration ensures that NLB can be dynamically configured and adjusted as your application scales or changes over time. For containerized deployments, NLB can route traffic directly to containers running in ECS, based on port-level rules.
DNS Failover Support
If the targets in one Availability Zone become unhealthy or the zone becomes inaccessible, NLB can trigger DNS-level failover using Amazon Route 53. This ensures that client requests are rerouted to healthy targets in other zones. With DNS failover, your application continues to be available even during partial service outages.
This feature supports the creation of resilient applications that operate effectively across multiple failure domains, reducing the impact of regional outages or infrastructure-level failures.
AWS Network Load Balancer Pricing
The pricing model of AWS Network Load Balancer is based on several usage metrics, allowing for a scalable and pay-as-you-go model. The key components of NLB pricing include:
Load Balancer Capacity Units (LCUs)
AWS measures NLB usage in LCUs. One LCU includes the following dimensions:
- 25 new connections per second
- 3,000 active connections
- 1 GB of data processed per hour
- 1,000 rule evaluations per second (for TLS listeners)
Your NLB usage is charged based on the highest dimension used among these four. For example, if your application handles more new connections per second than it transfers data, you’ll be billed based on connection count.
Hourly Charges
An hourly fee applies for each active Network Load Balancer. The fee varies by AWS region and is added to the cost of the LCUs consumed.
Data Processing Charges
Each GB of data transferred through the load balancer incurs a data processing fee. These costs are incurred regardless of the direction of the data (inbound or outbound).
Elastic IP Charges
Elastic IP addresses attached to your NLBs are billed per hour. While the cost is minimal, it can add up in large-scale, multi-zone deployments with many static IPs.
Cross-Zone Load Balancing Charges
If cross-zone load balancing is enabled, additional charges apply for traffic that flows between Availability Zones. This is particularly important for applications deployed across multiple zones and can influence design decisions depending on your budget constraints.
Free Tier
AWS offers a free tier for new users, which includes 15 LCUs per month for the first 12 months. This can be useful for experimentation and testing without incurring immediate costs.
Advantages of AWS Network Load Balancer
AWS Network Load Balancer is optimized for specific use cases and brings several key benefits to infrastructure and application management.
TLS Offloading
One major benefit of NLB is its ability to handle TLS termination. This means NLB can manage the decryption and encryption of HTTPS traffic, offloading this task from backend servers. It reduces the compute burden on your targets, improves performance, and simplifies certificate management by using AWS Certificate Manager.
This feature is critical in high-security environments or for companies that require centralized control over encryption protocols and key management.
Sticky Sessions with Source IP Affinity
NLB supports sticky sessions based on source IP. This feature ensures that traffic from a client is routed to the same backend target during the session, which is important for stateful applications. The affinity is managed at the target group level and allows for consistency in session data and behavior.
This approach is less complex than cookie-based stickiness used by ALB, which relies on application-layer data.
Low Latency and High Throughput
Because it operates at Layer 4 of the OSI model, NLB introduces minimal processing overhead. This enables near-instantaneous response times and high throughput, supporting millions of requests per second.
This performance is beneficial for time-sensitive workloads such as financial trading platforms or real-time analytics engines.
Elastic IP Support
NLB allows you to assign static IPs to each Availability Zone, making it easy to whitelist IPs with external vendors, regulatory bodies, or firewall appliances. This is especially useful in industries where fixed IP addressing is required for compliance and auditing.
NLB is the only load balancer in AWS that natively supports Elastic IP addresses, giving it an edge in scenarios where static IPs are a requirement.
Persistent TCP Connections
Applications that require persistent connections, such as chat applications, multiplayer games, or telemetry services in IoT, benefit significantly from NLB’s support for long-lived TCP sessions. These connections can persist for months or even years without interruption.
With low idle timeouts and no need to frequently re-establish connections, applications enjoy stable and reliable communication channels.
Disadvantages of AWS Network Load Balancer
Despite its powerful features, AWS Network Load Balancer also has some limitations that can impact specific use cases or deployment strategies.
Lack of SSL Offloading at Layer 4
Because NLB is fundamentally a Layer 4 load balancer, SSL/TLS offloading is only supported through dedicated TLS listeners. Compared to Application Load Balancer, which operates at Layer 7, NLB lacks advanced content-based routing capabilities.
It does not inspect HTTP headers, cookies, or URL paths, so it’s not suitable for use cases that require granular request routing.
No Session Persistence Beyond Source IP
While NLB does support source IP affinity, it does not provide full-fledged session persistence mechanisms found in Layer 7 load balancers. There are no application-aware mechanisms like sticky cookies, so use cases requiring deep session management may face limitations.
This could affect applications where session data is tightly coupled with a user or where session tracking needs to span across IP address changes.
No Intelligent Load Redistribution
NLB lacks intelligent rebalancing capabilities. If a target becomes overloaded but remains healthy, the NLB will continue sending traffic based on the original hashing logic. This can lead to uneven load distribution and potentially degrade application performance during sudden spikes in traffic.
You may need to implement custom logic on the backend or combine it with Auto Scaling to mitigate this issue.
Limited Visibility Into Traffic Content
Since NLB operates at Layer 4, it cannot provide visibility into the application-level content of traffic. This limits its utility in debugging application behavior or monitoring API performance. Logging and monitoring have to rely on external tools like CloudWatch Logs or VPC Flow Logs.
This contrasts with Application Load Balancer, which provides detailed logs of request headers, response times, and routing rules.
Higher Cost in Some Scenarios
For low-throughput or simple applications, NLB may be more expensive than other AWS load balancing options due to its pricing model based on LCUs and additional data processing charges. If an application only requires basic routing without the performance benefits of NLB, other solutions might be more cost-effective.
Use Cases of AWS Network Load Balancer
AWS Network Load Balancer is specifically designed for applications that require high performance, extremely low latency, and the ability to maintain long-lived TCP or UDP connections. Below are several practical use cases where NLB is a suitable solution.
Real-Time Gaming Applications
Online multiplayer games depend heavily on real-time data exchange and low-latency communication. Network Load Balancer supports both TCP and UDP, making it ideal for routing game traffic to game servers with minimal delay. The persistent connections help maintain smooth gameplay without disconnections or lags.
Internet of Things (IoT)
IoT devices often maintain long-lived TCP sessions with backend systems to push telemetry or receive updates. Network Load Balancer is optimized to handle millions of connections simultaneously, ensuring reliable communication between devices and cloud applications.
Financial Services
Applications in financial markets require extremely low latency and high reliability. Whether for trading platforms, real-time market feeds, or payment gateways, NLB ensures data is delivered quickly and connections are reliably managed without interruptions.
Healthcare Applications
Medical imaging platforms, patient monitoring systems, and health data analysis platforms often need secure and uninterrupted connections. NLB can be configured with TLS to protect sensitive data in transit and support high availability for compliance-critical environments.
High-Traffic Web Applications
For applications that receive millions of requests per second, especially those that rely more on transport-layer rather than application-layer logic, NLB is a reliable choice. Examples include DNS resolvers, proxy servers, and media streaming backends.
Best Practices for Using AWS Network Load Balancer
To maximize the benefits of Network Load Balancer and ensure reliability, scalability, and performance, it’s important to follow architectural and operational best practices.
Deploy Across Multiple Availability Zones
To ensure fault tolerance and high availability, configure the NLB across at least two or more Availability Zones. This setup ensures that even if one zone fails, the application continues to function using the healthy targets in the other zones.
Use Target Groups Effectively
Target groups allow logical grouping of instances based on their purpose, port, or service. For example, grouping ECS containers by service type or EC2 instances by function helps manage health checks and routing more efficiently. Assign appropriate health check paths and intervals based on each group’s behavior.
Enable Cross-Zone Load Balancing
If your backend application does not use equal capacity across zones, consider enabling cross-zone load balancing. It ensures even distribution of traffic across all targets, regardless of which zone the client request originates from. Be mindful of the additional cost due to inter-zone data transfer.
Optimize Health Check Configuration
Configure health checks according to the responsiveness and behavior of your targets. For example, backend services with occasional delays may need longer timeout values or fewer threshold failures to avoid being marked unhealthy prematurely.
Use TCP-based health checks for low-overhead monitoring or switch to HTTP checks when more detailed evaluation is needed.
Integrate with Auto Scaling
Combine NLB with EC2 Auto Scaling to dynamically adjust capacity based on demand. NLB will automatically register new instances and deregister terminated ones as they join or leave the target group, ensuring smooth traffic distribution.
Security Considerations
Security is an integral part of deploying and operating load balancers. AWS Network Load Balancer supports several features and configurations to maintain the confidentiality, integrity, and availability of your applications.
Use AWS Certificate Manager (ACM) for TLS Termination
For secure communication over the internet, configure TLS listeners and use ACM to manage SSL/TLS certificates. This approach simplifies the certificate renewal process and ensures traffic between clients and the load balancer remains encrypted.
TLS termination also allows backend services to operate on decrypted traffic, reducing processing overhead on your servers.
Maintain Source IP Visibility
Unlike other load balancers, NLB preserves the source IP address of the client. This is important for logging, analytics, security monitoring, and IP-based access control.
Ensure that your backend services are designed to read the source IP address directly from the network layer.
Use Security Groups and Network ACLs
Even though NLB itself doesn’t require security groups, backend instances or containers must be protected using security groups and Network ACLs. Define rules that allow only the necessary traffic based on port, IP range, and protocol to minimize the attack surface.
Logging and Monitoring
Enable VPC Flow Logs and use AWS CloudWatch for monitoring the performance and health of your load balancer. Set up alarms for unusual patterns such as spikes in failed health checks or drops in connection counts to trigger early warnings.
Apply Principle of Least Privilege
When granting permissions to users or services managing the NLB, use IAM roles and policies that follow the principle of least privilege. Allow only the necessary API actions to avoid accidental misconfigurations or security breaches.
Comparison with Other AWS Load Balancers
AWS offers multiple types of load balancers. Choosing the right one depends on your application’s architecture, traffic type, and operational requirements.
Network Load Balancer vs Application Load Balancer
Network Load Balancer operates at Layer 4 and is designed for ultra-low latency, handling TCP/UDP traffic and TLS termination. It is suitable for applications requiring high performance and minimal processing overhead.
Application Load Balancer operates at Layer 7 and is optimized for HTTP and HTTPS traffic. It allows advanced routing features based on URL paths, host headers, query parameters, and cookies. ALB is better suited for web applications, APIs, and microservices that require intelligent request routing.
Use ALB when you need fine-grained control over traffic routing and visibility into HTTP headers. Choose NLB when performance and connection management are more critical.
Network Load Balancer vs Classic Load Balancer
Classic Load Balancer is the legacy option and supports both Layer 4 and Layer 7 with fewer features. It is being phased out in favor of ALB and NLB. NLB offers better performance, scalability, and pricing compared to Classic Load Balancer.
Unless you are maintaining legacy applications, it’s recommended to migrate away from Classic Load Balancer to newer options like NLB or ALB.
When to Use NLB
Choose AWS Network Load Balancer when:
- Your application requires millions of concurrent connections with low latency
- You need to maintain long-lived TCP or UDP sessions
- Source IP preservation is required for auditing or application logic
- You need to assign static IP addresses (Elastic IPs) for whitelisting or compliance
- Your workload is latency-sensitive and does not require Layer 7 features
Avoid using NLB when your application needs deep HTTP routing, user session tracking using cookies, or real-time header-based routing decisions.
Final Thoughts
AWS Network Load Balancer stands out as a high-performance, low-latency solution tailored for demanding network-level traffic. It was designed with scalability, availability, and reliability at its core, making it a valuable component for modern, large-scale applications that rely on consistent and stable network connections.
Unlike traditional load balancers that primarily serve web-based traffic at the application layer, NLB operates at the transport layer. This means it can handle massive volumes of TCP and UDP traffic efficiently without introducing significant processing overhead. Its ability to manage millions of connections simultaneously, maintain persistent TCP sessions, and support TLS offloading positions it as a strategic choice for specific use cases such as gaming, IoT, financial systems, and backend APIs that do not require complex routing logic.
The support for features like Elastic IPs, zone-based isolation, and native integration with other AWS services such as ECS, Auto Scaling, and Certificate Manager further enhances its usability and simplifies infrastructure management in the cloud.
That said, NLB isn’t always the right choice. For scenarios that demand deep packet inspection, header-based routing, user session affinity using cookies, or advanced HTTP behavior, Application Load Balancer or even API Gateway might be more appropriate. Therefore, understanding your workload’s specific needs is critical before selecting a load balancing solution.
From a cost perspective, NLB provides a pay-as-you-go pricing model that allows organizations to scale their traffic routing solutions as needed. When managed correctly using best practices—such as proper health check configuration, multi-zone deployment, and effective use of security controls—NLB delivers high return on investment while reducing infrastructure complexity.
In summary, AWS Network Load Balancer is not just a technical utility but a strategic resource for building robust, scalable, and performant systems on the cloud. It empowers businesses to meet the growing demands of modern applications while maintaining the agility and reliability that cloud-native architectures require.