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/AWS ELB lots of 5xx when facing high peak/

AWS ELB lots of 5xx when facing high peak


I am experiencing a high number of ELB 5xx errors where it did not forward the traffic to my ECS targets, during a high peak where access went up from 10k to 60k per minute.

After research we are quite confident that it is not anything in here: And also the ECS service itself is running well. Anyone has any idea what could be the bottleneck for ELB?

  • Could you please clarify which 5xx you saw? 502, 503, 500 or other? When 5xx error occurred, can you check if all ECS targets are healthy and reachable?

1 Answers

You may be experiencing a ramp up so fast the ALB is not scaling fast enough. Look at the following metrics:


If you are using a Classic Load Balancer, Look at the following metrics:


If you see that you are not scaling fast enough, you can work with support to "pre-warm" the load balancers by filing a support ticket.

answered 22 days ago
reviewed 21 days ago

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