Have a solid, standardized base/framework layer for your services, and a way to roll out changes to it that doesn’t involve manual work for each service. Migrations are the devil. You will have an extraordinarily difficult time evolving cross—cutting concerns like auth, tracing, metrics, profiling, health checking, RPC encoding, discovery and routing, secrets, etc. without it.

And definitely don’t start migrating stuff that matters until you have mature implementations and operations around all those things, and probably many others too.