performance-audit

Performance Audit

Diagnostic Commands

# Enabled modules count — over ~100 on a simple site suggests module bloat
ssh web drush pm:list --status=enabled --format=list | wc -l

# Recent PHP errors — repeated warnings/notices on every request cost performance
ssh web drush watchdog:show --type=php --count=20

# Slow queries counter — a value > 0 that grows on reload means slow SQL to investigate
ssh web drush sqlq "SHOW STATUS LIKE 'Slow_queries'"

For function-level profiling, use the xdebug-profiling skill.

Baseline Measurement (do this BEFORE and AFTER any change)

# Page timing from inside the web container (timing measurement only — this is
# NOT functional testing; functional testing still uses Playwright, never curl):
ssh web curl -s -o /dev/null -w "first: %{time_total}s\n" http://localhost/PATH
ssh web curl -s -o /dev/null -w "second (warm cache): %{time_total}s\n" http://localhost/PATH

Record both numbers. After your fix, re-run and compare — if there is no measurable improvement, the bottleneck is elsewhere.

How to Detect N+1 Queries

1. Profile the slow page with the xdebug-profiling skill (profile mode).
2. In the analyzer output, look for entity load / query functions with a very high call COUNT (e.g. Drupal\Core\Entity\...::load called 200 times).
3. Find the loop in the code calling load() per item and replace with loadMultiple().
4. Alternative: if the devel/webprofiler module is installed, enable its DB query log and look for many near-identical queries.

Caching Strategy

Cache Tags (What to invalidate)

$build['#cache']['tags'] = ['node:123', 'node_list'];

// Custom tags
$build['#cache']['tags'] = Cache::mergeTags(
  $entity->getCacheTags(),
  ['mymodule:custom_list']
);

Cache Contexts (When to vary)

$build['#cache']['contexts'] = [
  'user.permissions',
  'user.roles:authenticated',
  'url.query_args',
  'languages:language_content',
];

Cache Max-Age

$build['#cache']['max-age'] = 3600;          // 1 hour
$build['#cache']['max-age'] = 0;             // Never cache (use sparingly!)
$build['#cache']['max-age'] = Cache::PERMANENT; // Until invalidated