I'll color the picture in a little more, maybe that will help make sense of it.
We have a unique workload that includes very large bursts of work that need to be worked on ASAP. Spinning up instances on demand is not fast enough, so we had a lot of servers sitting idle. Lambda allows us to execute this same work for much cheaper because we aren't paying for idle CPUs. Lambda also allows us to execute at much higher concurrency than ec2 would, for the cost. 15000 Threads spread across 100's of IPs is easy and cheap on lambda, not so much on EC2.
We went from ~250 customers per cluster(our term for a set of dedicated workload servers) to 2600(haven't pushed it past there yet). The work that was done on those instances is slowly being moved to Lambda and all new work/features are added to Lambda directly. This has effectively allowed us to drop a few clusters and also move to lower resources per instance.
FWIW we don't use ELB for Lambda, they come in via API Gateway, to Lambda/Step Functions directly or into an SQS queue in the case of workloads that have rate limits. For Lambda based workloads it breaks down something like 56% of cost is Lambda, 34% of cost is Step Functions and 9% is API Gateway.
We have a unique workload that includes very large bursts of work that need to be worked on ASAP. Spinning up instances on demand is not fast enough, so we had a lot of servers sitting idle. Lambda allows us to execute this same work for much cheaper because we aren't paying for idle CPUs. Lambda also allows us to execute at much higher concurrency than ec2 would, for the cost. 15000 Threads spread across 100's of IPs is easy and cheap on lambda, not so much on EC2.
We went from ~250 customers per cluster(our term for a set of dedicated workload servers) to 2600(haven't pushed it past there yet). The work that was done on those instances is slowly being moved to Lambda and all new work/features are added to Lambda directly. This has effectively allowed us to drop a few clusters and also move to lower resources per instance.
FWIW we don't use ELB for Lambda, they come in via API Gateway, to Lambda/Step Functions directly or into an SQS queue in the case of workloads that have rate limits. For Lambda based workloads it breaks down something like 56% of cost is Lambda, 34% of cost is Step Functions and 9% is API Gateway.