Design Better Data Layers

Schema planning

Start from access patterns, not ER diagrams drawn for their own sake. Capture cardinality, write skew, and deletion semantics before you argue about normal form. We ask for a one-page “table contract” per feature: primary key story, foreign keys, invariants, and the first three queries you expect.

• Explicit nullable decisions tied to user-visible behavior.
• Migration sequences that roll forward safely on multi-tenant schemas.
• Check constraints where they replace easy-to-bypass application-only validation.

Query tuning process

Hypothesis before indexes. Capture the business question, the smallest reproducer, and the plan diff when you change one variable. We discourage screenshot-only posts in mentor threads — attach the predicate, the row estimate, and what you already tried.

1. Reproducer SQL + parameters frozen.
2. Plan + buffers where supported.
3. Single change + retest + short note.

Resilience strategies

Backups without restore drills are folklore. Replication without lag monitoring is hope. Pair each technical control with a human-readable run step: who runs it, how long it should take, and what “green” looks like.