Comparing a new implementation against an old one is only a test while the old one stands still.

👋 Hi, I'm Anton - a software engineer working mostly in PHP/Symfony and Go, currently carving a live PHP monolith into Go services. This series is about one write path that left the monolith and what it took to accept it as working. This part is about checking a migration while both sides keep moving - and about response codes that describe the wire rather than the storage. Running notes live on my GitHub: github.com/brilliant-almazov .

This is how I do it right now, with the price attached - maybe you already do it better, maybe you'd do it another way.

Where the boundary was drawn

The migration moved computation out of the monolith before it moved data .…