HighFile-scopeJava Plug & play

Optimize database queries with proper indexing

Index columns used in JOIN/WHERE/ORDER BY; verify plans and avoid full scans for hot queries.

Why this matters

Indexes drastically reduce query latency and lock contention.

Side-by-side examples engineers can pattern-match during review.

Avoid

-- filtering by email with no index
SELECT * FROM users WHERE email = ?;

Prefer

CREATE INDEX ix_users_email ON users(email);
SELECT id FROM users WHERE email = ?;

Bad

WHERE email=? on unindexed col

Good

CREATE INDEX ...

From the same buckets as this rule.

Critical
Block risky database migrations (locking ops, downtime risk)
Review SQL/database migrations for operations that can lock large tables or cause downtime. Examples: creating indexes without CONCURRENTLY (Postgres), ALTER COLUMN TYPE on big tables, adding NOT NULL without backfill, long-running updates without batching. Require an online migration strategy (CONCURRENTLY, backfill in batches, dual-write/expand-contract) and a rollback plan.
migrations-backward-compatdatabase-query-performance
High
Add database indexes for query optimization
Index frequently filtered or joined columns and verify with query plans.
database-query-performanceperformance-efficiency
High
Add database indexes for query performance
Index columns used in WHERE/JOIN/ORDER and enforce uniqueness where applicable.
database-query-performance