Distributed Systems

A hot cache key expires and a hundred requests issue the same query at once, saturating the database. Go's singleflight package coalesces those duplicate calls into one. How to wire it up, how to measure whether it's firing, and why per-pod coalescing is usually enough.

PostgreSQL 19's new WAIT FOR LSN command lets a replica block until it has replayed your write. The read-after-write problem it solves, the workarounds it replaces, and what the timeout, status, and mode options are actually for.

Key takeaways from Amazon's 2007 Dynamo paper.

Why logging at every layer of a service produces noise, and how to log only at the handler level while propagating context from below.

How to test unary gRPC services in Go - handler logic, interceptors, deadlines, metadata propagation, and rich error details - all in-memory with bufconn.

Why the middleware-to-handler boundary is a special case for context values.

A simple litmus test for when to use context values in Go.

How to wrap a generated gRPC client behind a clean Go API so users never have to touch protobuf types or connection management directly.

Why the etcd codebase is my go-to reference for building gRPC services in Go.

Master shadow testing for large-scale system migrations. Learn to safely rewrite services by comparing outputs between old and new implementations.

Separate business logic from external service calls using the Gateway pattern. Apply dependency inversion and interface segregation in Go.

Deep dive into event-driven architecture patterns. Learn publish-subscribe, CQRS, outbox pattern, eventual consistency, and handling microservice coupling.

Define service contracts with Protocol Buffers for non-gRPC systems. Generate serializers, maintain self-documented APIs, and ensure cross-language compatibility.