I think the current best practice is 'monolith-first' - but try to use a framework that allows you to isolate domains/logic (like rails engines or django apps)

I think the current best practice is 'monolith-first' - but try to use a framework that allows you to isolate domains/logic (like rails engines or django apps). Then once you grow to a suitable size where it makes sense break it up. My experience was, with a smaller shop, it was kinda hard to automate all the stuff you do when starting a new app - it may need stuff like: github repo, permissions, airbrake api key, docker hub repo, added to the CI tool, added to the static analysis tool, alerting/monitoring config, etc. You also need a way to enforce global org requirements like, "all apps need to log in JSON so it be easily parsed later for analysis." or "all apps should expose a health check at /health-check" or "all apps need to use version X of dependency Y because of a security issue". Without this automation your apps begin to drift in standards and practices. They accumulate old libraries and it becomes a lot harder to, say, move from one CI tool to another.