ALB vs NLB
What does Loadbalancer do?
- The load balancer acts as the entry point into your system.
- The listener listens for incoming connections
- The load balancer forwards requests to a target group.
- The target group consists of one or multiple targets.
- A target might be an EC2 instance, container, or internal service.
- The health check monitors the targets.
How to decide if ALB vs NLB suits you better? Consider the below points before making your decision
Do clients connect via UDP or non-HTTP?
If clients utilize a protocol other than HTTP/1.1, HTTP/2, or gRPC to connect with your application, the Application Load Balancer (ALB) will not be suitable. In such cases, the Network Load Balancer (NLB) becomes necessary. For instance, scenarios involving UDP communication exclusively necessitate the use of an NLB. Furthermore, if you intend to employ HTTP/3, the NLB is currently the sole option available to you.
Do you need to optimize for performance?
The Application Load Balancer (ALB) operates at layer 7 of the network stack, allowing it to examine the specific details of each incoming HTTP request. In contrast, the Network Load Balancer (NLB) operates at layer 4, focusing solely on forwarding incoming TCP or UDP connections to designated targets. Unlike the ALB, the NLB does not inspect the content or specifics of an incoming HTTP request. Its primary role is to facilitate the routing of TCP or UDP connections without diving into the intricacies of higher-level protocols.
Due to its simplified role and focus, the Network Load Balancer (NLB) requires less processing compared to an Application Load Balancer (ALB). Consequently, the NLB can forward incoming requests with lower latency. Therefore, when optimal performance is a critical consideration for your workload, utilizing an NLB becomes an advantageous choice to minimize latency and enhance overall response times.
Do you expect unpredictable traffic spikes in ALB vs NLB?
The Application Load Balancer (ALB) is capable of automatically adapting to increased connections and requests. However, this scaling process may take several minutes to complete. Consequently, when anticipating significant traffic spikes, the ALB might not be able to scale rapidly enough to handle the sudden surge of incoming requests in a timely manner. AWS recommends notifying their support team in advance if you expect a substantial traffic spike, as they can pre-warm the ALB to mitigate the issue. However, this approach is effective only when traffic spikes can be predicted.
On the other hand, the Network Load Balancer (NLB) does not require scaling the number of nodes responsible for processing incoming connections. It is specifically designed to handle unexpected and substantial traffic spikes efficiently.
Therefore, when anticipating unpredictable and substantial traffic spikes, the NLB is a more suitable choice. It is important to note that AWS does not explicitly define what constitutes a “huge traffic spike.” For most applications, the capabilities of an ALB will be more than sufficient. However, scenarios such as a sudden influx of traffic resulting from a Super Bowl ad directing users to your web application or the release of a highly anticipated product like the new PlayStation in your online shop may pose challenges that require careful consideration and utilization of the NLB.
Do you need static IP addresses for inbound traffic?
When establishing a connection to an Application Load Balancer (ALB), clients rely on resolving its dynamic DNS name. As the IP addresses associated with the ALB can change over time, it may not be suitable when static IP addresses are required for inbound traffic. Fortunately, the Network Load Balancer (NLB) offers a solution by providing static IP addresses by default. This feature is particularly beneficial in scenarios where a third party requires static IP addresses for creating firewall rules or when a client lacks the ability to resolve hostnames and necessitates direct IP address connectivity.
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