I've got an RDS instance (db.t2.micro - 1 vCPU, 1GiB RAM) that I'm spamming with connection attempts to mimic high load on the DB over a short period of time and am consistently hitting a DB connection limit of ~100 regardless of the DB instance class (I've tried db.t2.large - 4 vCPU, 16GiB RAM), setting the 'max\_connections' parameters as part of a custom parameter group and the use of an [RDS proxy](https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/rds-proxy.html) for connection pooling.

I do notice that the red line on the DB connections graph below disappears when I increase the DB instance class which looks like more connections should be available but as can be seen in the graph the connection limit is pretty fixed at ~100

I've read threads where people have DB connections into the 000s and 0000s even so I'm convinced I'm missing something here on the configuration side of things, any ideas?

[![RDS DB connections](https://i.stack.imgur.com/FUElt.png)](https://i.stack.imgur.com/FUElt.png)

**Edit:** I am able to exceed ~100 connections if using the JDBC library but when I use mimic our production system which is a REST API running as a service on AWS ECS, I max out at ~100, with a http 500 error
[![RDS db conns](https://i.stack.imgur.com/wLruE.png)](https://i.stack.imgur.com/wLruE.png)
[![http 500](https://i.stack.imgur.com/wFei1.png)](https://i.stack.imgur.com/wFei1.png)

The CloudWatch log indicates the 'rate exceeded'. The REST API is built using Microsoft.NET.Sdk.Web. In my use case the server needs to be able to handle ~500 API requests a second every 15mins.
[![enter image description here](https://i.stack.imgur.com/PxnCq.png)](https://i.stack.imgur.com/PxnCq.png)