Less frequently used endpoints are more exposed to cold starts when not using a monolith

True but it’s worth asking oneself if this is really an issue for one’s use case - some metrics here https://mikhail.io/serverless/coldstarts/aws/languages/

Its not just pure coldstart it's also establishing a database connection pool. It's not a complete deal breaker but I am really focused on building a snappy application and it hurts when a user perceives lag

Could RDS Proxy help you there?

Don't think it'll change the fact my application has to make connections to something

Yes, but the proxy will handle the pooling of connections, you’re just requesting the allocation of a pre-existing connection, rather instantiating a connection (or a connection pool) within your lambda

this one is the best article I know on cold starts when building big lambda functions (= lots of dependencies)