Will the optimization break my custom modules or extensions?

No, that’s the whole reason we use blue-green deploy. The optimised configuration is built and warmed up next to production, then we cut over in < 30 seconds. The old config stays warm for 72 hours, so if anything regresses we flip back instantly. We also do a regression QA pass on staging covering: critical extension flows (search, faceted nav, custom checkout steps, payment gateways), the admin panel, and any custom REST/GraphQL endpoints. The audit catalogues every extension on your store and flags risky ones before any work starts, you sign off the scope, not us.