“EN-09-Full-Stack-Project-Implementation”

Multi-tenancy strategy comparison (shared schema + tenant_id vs schema-per-tenant)

The 8 most important queries as SQL with EXPLAIN ANALYZE expectations; write

Migration plan: expand/contract (additive, backfill, switch, drop) with

SQL Query Debugger & Optimizer

Paste a slow query and get a diagnosis, rewritten SQL, and index recommendations with EXPLAIN-based reasoning.

Read the plan bottom-up; identify the dominant cost (seq scans, bad estimates,

Point out stale statistics or planner mis-estimates and the ANALYZE/VACUUM

Rewrite the query (CTEs vs subqueries, join order, semi-joins with EXISTS,

Provide exact CREATE INDEX statements (with CONCURRENTLY) and predict the

TypeScript Type System Solver

For difficult generic types, conditional/mapped types, and eliminating `any` safely. Outputs compile-safe types with explanations.

Usage examples showing correct calls and 4+ calls that SHOULD error — each with

Edge cases: optional props, unions of events, readonly tuples, and inference

Unit Test Engineer (Behavior-First)

Generates high-value tests: behavior tables, boundary cases, property-based tests, and failure injection — without testing implementation details.

Integration / E2E Test Architect

Designs deterministic end-to-end tests with fixtures, seeding, auth, and CI parallelization for web apps/APIs.

Test pyramid plan: which behaviors belong in unit/integration/E2E; keep E2E

Deterministic environment: docker-compose/testcontainers with real {{Postgres,

Data strategy: per-test isolated schema/database, factory-based seeding, no

Flake defense: auto-waiting locators, no hard sleeps, network-idle avoidance,

Write 5 example E2E specs (login, create resource, validation errors,

Git / Debugging Incident Responder

When something broke after a change: bisects commits, reads traces, and proposes root cause + fix + regression test. Replaces random "try this" debugging.

Experiments to falsify each hypothesis (commands, queries, logs, git bisect