Recent discussion about their tech stack: https://stackoverflow.blog/2021/03/30/roberta-arcoverde-stac...

Summary: simple as possible, maintainable, no micro-service hell - just a bunch of boxes serving with the cache and highly optimized SQL queries. Know your storage engine.

This is yet another example that not getting bogged down in cargo cults, micro-services, and instead solving problems you have will result in a smaller, more agile team, leaner infrastructure bill and burn rate, and a higher chance of a successful exit.