# Fix patterns by bottleneck category

Load this file once `references/diagnostic-tools.md` (or the Step 3
baseline metrics) has pointed at a dominant bottleneck. Pick *one*
primary category to fix at a time — trying to fix everything in one pass
makes the before/after Verification step in `SKILL.md` meaningless, since
you won't know which change caused which delta.

Every fix below is still gated by `SKILL.md`'s Step 0 (read-only-first)
and Verification (re-measure the same way afterward) sections.

## Database / query performance

Use when profiling points at DB time or a high query count.

- Avoid N+1 query patterns — batch queries, prime caches, avoid per-row
  lookups inside a loop.
- Prefer `fields => 'ids'` in `WP_Query`/`get_posts()` when only IDs are
  needed.
- Avoid expensive meta queries where possible; consider indexing or a
  schema change for genuinely hot lookups.
- Use object caching for repeated reads (see below) rather than
  re-querying the same data every request.

Backend-only tools: Query Monitor via REST (query lists, stack traces,
slow/duplicate flags) — see `diagnostic-tools.md`. `wp db query` for
targeted SQL/`EXPLAIN` — be careful running this in production, it's a
direct DB access path.

Query Monitor plugin: https://wordpress.org/plugins/query-monitor/

## Autoloaded options

Autoloaded options load on *every* request, so a large autoload payload
hurts every page, not just the page that set the option.

Quick checks (see `SKILL.md` Step 3 for the always-collect total):

```bash
wp option list --autoload=on --fields=option_name,size_bytes | sort -n -k 2 | tail
```

Fix patterns:

- Stop autoloading large blobs — store large/rarely-read data with
  `autoload=off` instead.
- Move large computed data to transients or the persistent object cache
  (if the site has one — check first, see `SKILL.md` Step 3 metric 3)
  rather than an autoloaded option.
- Remove stale options left behind by removed plugins/themes — confirm
  nothing still reads the option before deleting; a stale-looking option
  name isn't proof nothing depends on it.

Docs: `wp option list` — https://wpcli.dev/docs/option/list · `wp doctor`'s
`autoload-options-size` check —
https://make.wordpress.org/cli/handbook/doctor-default-checks/

## Object caching

Use when profiling shows repeated identical queries or a low cache hit
rate.

- WordPress's default object cache is per-request memory only — it does
  not persist across requests unless a persistent drop-in
  (`wp-content/object-cache.php`) is present. On this fleet, that's
  currently only true for `menorca.pt`/`menorca.ro` (Redis Object Cache
  plugin against cerebro's Valkey) — see `SKILL.md` Step 3 metric 3
  before assuming a site has one.
- `wp cache flush` (or the Redis-plugin-specific `wp redis flush`) can
  affect more than the one site you're working on — cerebro's Valkey DB 0
  is genuinely shared across sites by key-prefix, not fully isolated per
  site (confirmed in `docs/server-cerebro.md`: `wp redis enable`'s
  `FLUSHDB` clears the whole shared DB 0, not just the calling site's
  prefix). Never flush without explicit approval.

Fix patterns:

- Cache expensive computed results (transients, or the persistent object
  cache where one exists) with explicit invalidation — don't rely on
  natural expiry alone for data that changes on a known event.
- Avoid unbounded caches — set expirations, or implement real
  invalidation hooks tied to the data changing.
- If a site doesn't have a persistent object cache and profiling
  genuinely points there, adding one is an infra change (provisioning
  Valkey ACL credentials on cerebro, installing the PHP Redis extension
  in the jail — package name `php85-pecl-redis`, not `php85-redis`, per
  `bastille-jail-provisioning`) — coordinate rather than doing it as a
  drive-by inside a performance investigation.

WP-CLI cache commands: https://wpcli.dev/docs/cache · flush guardrails:
https://wpcli.dev/docs/cache/flush

## Cron

Use when cron causes request-time spikes or slowness.

```bash
wp cron event list
wp cron test           # spawning health
wp cron event run --due-now
```

Fix patterns:

- De-duplicate scheduled events and reduce frequency where the task
  genuinely doesn't need to run that often.
- Ensure cron callbacks are idempotent and short — a task that's slow
  enough to matter for site performance is a candidate for moving off the
  request path entirely, not just running it less often.
- Move heavy work (imports, RSS/content-agent jobs — several granja sites
  already run these hourly, per `docs/server-granja.md`) fully off the
  page-load request path; a badly-timed spawn on a real WP-Cron pseudo-cron
  setup can add real latency to whichever request happens to trigger it.

WP-CLI cron command package: https://github.com/wp-cli/cron-command

## Remote HTTP API calls

Use when profiling shows slow external requests (`wp_remote_get()` etc.).

Fix patterns:

- Add explicit timeouts and fail-fast behavior — a slow or hanging
  third-party API shouldn't be able to make every page load slow.
- Cache responses where the data doesn't need to be live on every request
  (transients / persistent object cache where available).
- Batch requests, and avoid calling a remote API on every page load when
  a periodic cron-driven refresh would do.
- Move genuinely heavy remote work off the request path entirely (cron or
  a queue), same principle as the Cron section above.

Query Monitor can report HTTP API call timing via the REST envelope
(`qm` property) — see `diagnostic-tools.md`.