I Migrated a Product from AWS to GCP — Here's What I'd Do Differently

Three that actually hurt us:

Migrate and refactor separately. When something breaks mid-migration you won't know which change caused it. Move first, clean up after.

Don't assume equivalent services behave the same. SQS and Pub/Sub are both "message queues." The delivery guarantees and retry behaviour are different enough to surprise you.

Write a rollback plan per service, not just for the database. When a Cloud Run service had issues post-deploy, we were improvising. A one-page runbook per service removes the stress.

Good rule of thumb: if a decision feels rushed mid-migration, it probably is.