Amazon employee here. I can confirm that ALB and NLB do not need prewarming for most customers.
If you are Epic Games running Fortnite on AWS, and you want to direct millions of player connections through a brand new, freshly provisioned load balancer then you should definitely talk to support to make sure the load balancer is prewarmed and ready for that level of traffic.
But 99.99% of websites and service won't need intervention or prewarming at the load balancer level because the load balancer can and will scale up far faster than your backend server provisioning and scaling, or your database will. You only need to worry about prewarming a load balancer in the very specific conditions where you are immediately redirecting millions of active connections over to a new load balancer, and frankly there are very few companies that have that problem.
Additionally even if you do have that problem Amazon gives you the tools to solve it without needing any manual prewarming. Any blue/green traffic switchover at massive scale should probably use a weighted Route 53 DNS record set. You wouldn't immediately cut 100% of your traffic over to a new load balancer, instead you should dial it up in percentage increments while testing and monitoring the new stack. ALB and NLB can autoscale up gracefully and automatically as you increase the DNS weight on the new DNS record.
Comments
Amazon employee here. I can confirm that ALB and NLB do not need prewarming for most customers.
If you are Epic Games running Fortnite on AWS, and you want to direct millions of player connections through a brand new, freshly provisioned load balancer then you should definitely talk to support to make sure the load balancer is prewarmed and ready for that level of traffic.
But 99.99% of websites and service won't need intervention or prewarming at the load balancer level because the load balancer can and will scale up far faster than your backend server provisioning and scaling, or your database will. You only need to worry about prewarming a load balancer in the very specific conditions where you are immediately redirecting millions of active connections over to a new load balancer, and frankly there are very few companies that have that problem.
Additionally even if you do have that problem Amazon gives you the tools to solve it without needing any manual prewarming. Any blue/green traffic switchover at massive scale should probably use a weighted Route 53 DNS record set. You wouldn't immediately cut 100% of your traffic over to a new load balancer, instead you should dial it up in percentage increments while testing and monitoring the new stack. ALB and NLB can autoscale up gracefully and automatically as you increase the DNS weight on the new DNS record.