A practical, opinionated guide to designing backend APIs. Covers request and response schema, offset and keyset pagination, BFF, server-driven UI, caching, versioning, naming, the new HTTP QUERY verb, WebSocket vs SSE, API security (auth headers, server-to-server auth, webhook receivers), and bulk data load APIs. Built around Relay, the same AI proxy system from the multi-tenant SaaS post, with REST and JSON as the running example and Go code throughout.

Ingesting PII is easy; cleaning it up is hard. Here is how to use ClickHouse's data masking policies and regex to redact sensitive logs in flight without killing your query performance.