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How Two-Phase Locking Keeps Concurrent Bank Transactions From Corrupting Your Data

Two transfers hit the same account in the same millisecond and one payment vanishes. This is the lost update, and it is why every payment ledger runs on a concurrency control layer. This article builds the theory from a fintech example up to two-phase locking (2PL): the transaction model, the math of conflict-serializability and the precedence graph, why the 2PL theorem guarantees correctness, pessimistic versus optimistic control in PostgreSQL, strict 2PL, and how deadlocks are detected and prevented.

Load Balancing Algorithms: Each One Fixes the Last One's Flaw

Spreading requests across N servers sounds like a one-liner: pick a server, send the request. Then one backend is slower, or bigger, or holds a session, and the naive choice falls apart. This walks the classic algorithms as a chain where each one exists to fix the previous one's blind spot: round robin, weighted, least connections, power of two choices, and consistent hashing, in Go, ending with the failure every tutorial forgets.

From RBAC to ReBAC: Migrating a Role System to OpenFGA Without Downtime

Roles work until someone says 'share just this document with just this person.' That is the day RBAC runs out of road. This is the practical migration: mapping role tables to relation tuples, running OpenFGA in shadow next to your SQL checks, backfilling safely, and only then unlocking the per-object sharing and hierarchy that roles never could. With the traps nobody warns you about.