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SQL & Databases for Builders

Schema design that survives refactors, index strategy that survives scale, and transactions that don't corrupt data at 3 a.m. Postgres-flavored SQL for people who ship.

9 lessons

Course Q&A

Schema Design That Survives

Constraints as contracts, keys and types that age well, and migrations that don't take the site down.

  1. 01Constraints Are Contracts: NOT NULL, CHECK, UNIQUE, FKThe database is the only place every write passes through — put your invariants there, not in app code.25mOpen
  2. 02Keys and Data Types That Age WellIdentity vs UUID, timestamptz always, numeric for money, text over varchar, and jsonb with discipline.25mOpen
  3. 03Zero-Downtime Migrations on Big TablesWhich ALTERs rewrite the table, lock_timeout discipline, CONCURRENTLY indexes, and the NOT VALID / VALIDATE dance.35mMembers

Indexes and Query Plans

How B-trees actually answer queries, how to read EXPLAIN output, and which indexes are worth their write tax.

  1. 01How B-Tree Indexes Actually Answer QueriesLeftmost-prefix rules, composite column order, covering indexes, and matching ORDER BY to index ordering.30mMembers
  2. 02Reading EXPLAIN Like an OperatorEXPLAIN (ANALYZE, BUFFERS): estimate vs actual, scan and join types, and buffers as the honest metric.35mMembers
  3. 03Index Strategy: What to Build and What to SkipPartial and expression indexes, covering trade-offs, auditing unused indexes, and cleaning up bloat.30mMembers

Transactions and Query Patterns

Isolation anomalies that ship, query patterns that become incidents, and lock discipline that prevents deadlocks.

  1. 01Transaction Isolation and the Anomalies That ShipLost updates, write skew, what READ COMMITTED actually guarantees, and the atomic fixes that work.40mPremium
  2. 02Query Patterns That Become Tomorrow's IncidentN+1, OFFSET pagination, unbounded reads, functions on indexed columns, wildcard LIKE, and SELECT * on hot paths.35mPremium
  3. 03Locks, Deadlocks, and Transactions That Stay ShortConsistent lock ordering, no I/O inside transactions, FOR UPDATE scoping, and the SKIP LOCKED queue pattern.35mPremium