How do I install the DB Optimization skill?

Run npx skillmds@latest add jdanigo/db-optimization in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is DB Optimization safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with DB Optimization?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is DB Optimization free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published DB Optimization?

jdanigo (@jdanigo) published this skill. Their other Agent Skills are listed on their SkillMD profile.

DB Optimization by jdanigo — Agent Skill

Name: DB Optimization
Author: jdanigo

DB Optimization

Use when the bottleneck is database-shaped — slow queries, lock timeouts, connection exhaustion, N+1 patterns, index questions, schema migrations on hot tables. Evidence-first DB playbook for PostgreSQL, MySQL/MariaDB, MongoDB, and Redis backing the db-performance-tuner agent.

jdanigo d053d67 3.2 KB Updated Sep 17, 2026

File contents

DB Optimization — EXPLAIN before you touch anything

Playbook for the DB half of the Hydraia perf route. The db-performance-tuner agent does the diagnosis; this skill sets the rules the route runs under.

Expand-contract migration protocol

Expand: add the new column/table/index alongside the old — additive, backward-compatible, online.
Dual-write + backfill: application writes both shapes; backfill history in batches (bounded, throttled, resumable).
Switch reads to the new shape behind a verified flag; watch metrics.
Contract: only after a full bake period, remove the old shape in a later release. Contract is its own plan task, never bundled with expand.

Index design guidance

Composite order: equality columns first, then range, then sort — match the query, not intuition.
Covering indexes to eliminate lookups for hot read paths; weigh write amplification (every index taxes every write).
Partial/filtered indexes for skewed predicates (WHERE deleted_at IS NULL).
Hunt UNUSED indexes too (pg_stat_user_indexes, sys.schema_unused_indexes) — dropping one is also an optimization.
The index is not always the answer: sometimes it is the query shape, the schema, or the caller (N+1, missing cache).

N+1 patterns per ORM family

Detection: a loop in code + per-iteration query in the log/profile. The agent cites the code location.
Fix families: eager loading (include/select_related/prefetch_related/preload), query batching (IN lists), dataloader pattern (GraphQL), denormalized read models for hot aggregates.

Pooling guidance

Pool size starts near connections = cores * 2 + effective_spindles (HikariCP heuristic) — not hundreds; queueing beats connection thrash.
Always set: acquisition timeout, idle timeout, max lifetime. Connection churn (open/close per request) is itself a finding.

Per-engine evidence commands

See the db-performance-tuner agent definition for the full read-only evidence list per engine (EXPLAIN variants, stat views, lock views, SLOWLOG). This skill and that agent must stay in sync — update both or neither.

---name: db-optimizationdescription: Use when the bottleneck is database-shaped — slow queries, lock timeouts, connection exhaustion, N+1 patterns, index questions, schema migrations on hot tables. Evidence-first DB playbook for PostgreSQL, MySQL/MariaDB, MongoDB, and Redis backing the db-performance-tuner agent.---# DB Optimization — EXPLAIN before you touch anythingPlaybook for the DB half of the Hydraia perf route. The `db-performance-tuner` agent does the diagnosis; this skill sets the rules the route runs under.<HARD-RULES>- Read-first: no change is proposed without its EXPLAIN plan, stat, or code evidence. Live DB unavailable → code/schema inference only, tagged UNVERIFIED, with the confirming commands listed for the human.- All write-shaped operations (create index, schema change, config change) are PLAN TASKS — reviewed, gated, never executed by a diagnosis agent.- Destructive or blocking operations (table rewrites, long locks) are flagged for explicit human approval in the plan; prefer and name the online variant per engine: `CREATE INDEX CONCURRENTLY` (Postgres), `ALGORITHM=INPLACE, LOCK=NONE` (MySQL), rolling index builds (Mongo).- Schema changes on live tables follow EXPAND-CONTRACT, no exceptions.- Redact literal data values from any plan/log excerpt that lands in a committed artifact.</HARD-RULES>## Expand-contract migration protocol1. **Expand:** add the new column/table/index alongside the old — additive, backward-compatible, online.2. **Dual-write + backfill:** application writes both shapes; backfill history in batches (bounded, throttled, resumable).3. **Switch reads** to the new shape behind a verified flag; watch metrics.4. **Contract:** only after a full bake period, remove the old shape in a later release. Contract is its own plan task, never bundled with expand.## Index design guidance- Composite order: equality columns first, then range, then sort — match the query, not intuition.- Covering indexes to eliminate lookups for hot read paths; weigh write amplification (every index taxes every write).- Partial/filtered indexes for skewed predicates (`WHERE deleted_at IS NULL`).- Hunt UNUSED indexes too (`pg_stat_user_indexes`, `sys.schema_unused_indexes`) — dropping one is also an optimization.- The index is not always the answer: sometimes it is the query shape, the schema, or the caller (N+1, missing cache).## N+1 patterns per ORM family- Detection: a loop in code + per-iteration query in the log/profile. The agent cites the code location.- Fix families: eager loading (`include`/`select_related`/`prefetch_related`/`preload`), query batching (`IN` lists), dataloader pattern (GraphQL), denormalized read models for hot aggregates.## Pooling guidance- Pool size starts near `connections = cores * 2 + effective_spindles` (HikariCP heuristic) — not hundreds; queueing beats connection thrash.- Always set: acquisition timeout, idle timeout, max lifetime. Connection churn (open/close per request) is itself a finding.## Per-engine evidence commandsSee the db-performance-tuner agent definition for the full read-only evidence list per engine (EXPLAIN variants, stat views, lock views, SLOWLOG). This skill and that agent must stay in sync — update both or neither.

Frequently asked questions