postgres

SQLAlchemy 2.0 from the production angle. The engine/session/transaction layering, the typed declarative, the identity map, the N+1 query problem, async-only gotchas (no lazy loading), savepoint nesting, and the connection-pool knobs that decide whether the backend survives load.

Transactions are a promise. Learn the ACID guarantees, the exact anomalies each SQL isolation level prevents or allows, why two-phase locking blocks and MVCC does not, and how Postgres uses row versions plus a transaction ID visibility check to give you snapshot isolation without holding a single read lock.

B+ trees are the workhorse of relational databases. Learn why their high fanout and shallow depth match disk perfectly, how point lookups and range scans work, the difference between clustered and secondary indexes, how covering indexes eliminate table lookups, and the hidden write cost of keeping indexes up to date.

Ship a full-stack app on Next.js 15: Prisma schema, migrations vs db push, the hot-reload-safe client singleton, Server Components reading data, Server Actions mutating it, useOptimistic, Auth.js, and a Vercel + Neon deploy.