Help Center/ Elastic Load Balance/ FAQs/ Load Balancers/ Does ELB Have a Limit on Concurrent Connections?
Updated on 2025-06-30 GMT+08:00
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Does ELB Have a Limit on Concurrent Connections?

  • For details about the maximum number of concurrent connections supported by a dedicated load balancer, see Specifications of Dedicated Load Balancers.
  • In the following scenarios, ELB use fullNAT to forward traffic. The maximum number of concurrent connections that a backend server can handle cannot exceed 200,000. If the number is exceeded, 5-tuple port resources may be insufficient, affecting your services.
    • TLS listeners forward service traffic.
    • HTTP/HTTPS listeners forward WebSocket traffic.

    If your service involves these scenarios, you can calculate the minimum number of backend servers based on the concurrent connections your service needs to handle.

    For example, if your service needs to handle 1 million persistent connections and a single backend server supports 200,000 concurrent connections, then you need to add at least five backend servers (1,000,000/200,000 = 5).

  • Each IP as backend servers can handle a maximum of 100,000 concurrent connections.
Parent topic: Load Balancers