We Went Zero-Trust and Our Deploy Frequency Dropped 34%

We rolled out zero-trust architecture across 60 microservices — mTLS, SPIRE workload identity, OPA policy enforcement, no static credentials. Security incidents dropped 87%. Deploy frequency dropped 34%, mean deploy time doubled from 22 to 47 minutes, and we burned roughly $340K in engineering productivity in year one. The mistake wasn't adopting zero-trust. It was treating it as a security project instead of a developer experience project. Start policies in warn mode, decouple certificate rotation from your deploy pipeline, and tell leadership the velocity cost before you start — not after the numbers show up in a sprint retrospective.