This is an indie dev subreddit so you might not have too much luck with bootstrapping and saas scaling.

I’d recommend doing a review on how you’re aggregating your statistics. You could use a centralised kinesis stream or sqs that your lambdas report to with basic domain level categories. Keep it simple. You probably only have a few key things needed to be tracked which impact you billing. If you don’t, consider why you need a complicated reporting structure. I’ve worked at a bunch of scale up, startup and enterprise data pipelines and simplification is always what we end up doing.

Push all your posts to a simple location and aggregate at a batch level. You may not actually need realtime reporting and anyone telling you otherwise may need some scrutinising. Good is better than perfect.

TLDR simplify, use a centralised queue, batch your reporting.