Yeah I've worked on a website built on a bunch of Lambdas - something like 150 Lambdas that tied themselves in knots with both HTTP requests and message queues.

I ended up moving a bunch of the logic into an ECS-hosted monolith. Probably cost a bit more (warm-up plugins meant that no customers still cost us money) but it vastly simplified things and made scaling up easier (can't set scaling thresholds with Lambda).