Thanks a lot for the insights! I have been able to achieve about 180 RPS off a t2.xlarge, a 1 instance t2.medium RDS, and a 1 instance t2.micro Elasticache which seems satisfactory for my use case (should I be getting more off this configuration?, it costs about 170 USD/month :/). During my time with testing different instance types, one thing I always noticed was that I got the best throughput when I had 1 web server container along with only 1 worker. If I added more, it would just slow down. If I understand correctly when the web server receives the request, it immediately caches it within Redis, and then the Cron instructs the workers to stream this over to the database from the cache. My cache usage seems very nominal on the console, the payloads I am delivering are about 100-200 KBs, and I do seem to hit the IOPS limit on my database. But since the web server simply puts the blob in the datastore, why do I lose throughput when I add more workers?
Also, this 1:1 ratio makes me think that if I am to scale this horizontally, I would be better off 1) Creating a load balancer and attach them to an autoscaling group of instances, each of which run 1 Web server, 1 Worker, and maybe 1 Redis container, but share an RDS cluster, rather than 2) Using container orchestration by EKS/ECS and scale on 1:1 ratio for servers and workers. Is this the correct way of going about this? Thanks again!