Fix TTFB in Drupal

# 1) Enable the three core caching modules
$ drush pm:enable page_cache dynamic_page_cache big_pipe -y

# 2) Confirm they are enabled and running
$ drush pm:list --type=module --status=enabled | grep -E 'page_cache|big_pipe'
# expected:
# BigPipe                        big_pipe                 Enabled
# Dynamic Page Cache             dynamic_page_cache       Enabled
# Internal Page Cache            page_cache               Enabled

# 3) Confirm cache max-age is not clamped to 0 in system.performance
$ drush config:get system.performance cache.page.max_age
# expected: >= 300 (seconds). If 0, anonymous caching is effectively OFF.

$ drush config:set system.performance cache.page.max_age 900 -y

# 4) Rebuild the container so the new modules register their services
$ drush cache:rebuild

<?php
// composer require drupal/redis
// composer require predis/predis  # (or install phpredis PHP extension)

// Point Drupal at the Redis instance
$settings['redis.connection']['interface'] = 'PhpRedis'; // or 'Predis'
$settings['redis.connection']['host']      = '127.0.0.1';
$settings['redis.connection']['port']      = 6379;

// Use Redis as the default cache backend
$settings['cache']['default'] = 'cache.backend.redis';

// Bootstrap needs a small subset of caches early; wire the class loader here
$class_loader->addPsr4('Drupal\\redis\\', 'modules/contrib/redis/src');
$settings['bootstrap_container_definition'] = [
  'parameters' => [],
  'services' => [
    'redis.factory' => [
      'class' => 'Drupal\\redis\\ClientFactory',
    ],
    'cache.backend.redis' => [
      'class' => 'Drupal\\redis\\Cache\\CacheBackendFactory',
      'arguments' => ['@redis.factory', '@cache_tags_provider.container', '@serialization.phpserialize'],
    ],
    'cache_tags_provider.container' => [
      'class' => 'Drupal\\redis\\Cache\\RedisCacheTagsChecksum',
      'arguments' => ['@redis.factory'],
    ],
    'serialization.phpserialize' => [
      'class' => 'Drupal\\Component\\Serialization\\PhpSerialize',
    ],
  ],
];

// Optional: keep the small, session-scoped bins in the DB if Redis eviction is aggressive
$settings['cache']['bins']['bootstrap']  = 'cache.backend.chainedfast';
$settings['cache']['bins']['discovery']  = 'cache.backend.chainedfast';
$settings['cache']['bins']['config']     = 'cache.backend.chainedfast';

; PHP 8.2 opcache settings tuned for a Drupal 10 site with contrib modules
opcache.enable=1
opcache.enable_cli=0

; Memory: 256 MB is comfortable for Drupal core + 100-200 contrib modules
opcache.memory_consumption=256

; Interned strings: bump for twig-heavy render pipelines
opcache.interned_strings_buffer=32

; File count: Drupal core alone touches ~5000 files; contrib modules add more
opcache.max_accelerated_files=20000

; Do not check file timestamps on every request in production;
; run drush cache:rebuild as part of the deploy to reset opcache instead
opcache.validate_timestamps=0
opcache.revalidate_freq=0

; Fail fast if opcache cannot start
opcache.fast_shutdown=1

; PHP 8.1+: enable the JIT tracing engine for CPU-bound render code
opcache.jit=tracing
opcache.jit_buffer_size=100M

; Log opcache warnings to a dedicated file for prod monitoring
opcache.error_log=/var/log/php/opcache-error.log

; ---
; Deploy hook (systemd or CI):
;   drush cache:rebuild && systemctl reload php8.2-fpm
; This clears both Drupal caches and opcache in one deploy step.

<?php
// composer require drupal/purge drupal/fastly
// drush pm:enable purge purge_ui purge_processor_cron purge_queuer_coretags fastly -y

// Fastly credentials in settings.php (never commit these; load from env)
$config['fastly.settings']['api_key']  = getenv('FASTLY_API_KEY');
$config['fastly.settings']['service_id'] = getenv('FASTLY_SERVICE_ID');

// Instant purge on content save; falls back to soft-purge for high-churn sites
$config['fastly.settings']['purge_method'] = 'instant';
$config['fastly.settings']['stale_while_revalidate'] = 60;
$config['fastly.settings']['stale_if_error']         = 3600;

// Tell Drupal it is behind a reverse proxy so it trusts X-Forwarded-* headers
$settings['reverse_proxy'] = TRUE;
$settings['reverse_proxy_addresses'] = ['127.0.0.1']; // populate from your Fastly IP list

// Emit surrogate keys so Fastly VCL can key cache entries on Drupal tags
$settings['http_response_headers']['Surrogate-Control'] = 'max-age=86400';

# Check purge queue processors are running
$ drush purge:processor:ls
$ drush purge:queue:stats

# Fire a manual test purge for a single node tag
$ drush purge:queue:add node:123
$ drush purge:queue:work
# expected: 'Processed 1 items' with no errors

# Watch a node edit trigger the queue (in a second terminal)
$ watch -n 1 'drush purge:queue:stats'
# edit node 123 in admin -> queue length should tick up, then drain

# 1) Rebuild Drupal caches and warm the site
$ drush cache:rebuild
$ curl -s -o /dev/null https://example.com/         # warm the homepage
$ curl -s -o /dev/null https://example.com/about    # warm a content page

# 2) Confirm both Drupal cache layers hit on the second request
$ curl -sI -H 'User-Agent: Mozilla/5.0' https://example.com/ | \
    grep -iE 'x-drupal-cache|x-drupal-dynamic-cache|cache-status|cf-cache'

# expected (warm):
# X-Drupal-Cache: HIT
# X-Drupal-Dynamic-Cache: HIT
# Cache-Status: Fastly; hit
# (or) cf-cache-status: HIT

# 3) If X-Drupal-Cache stays MISS, look for max-age=0 emissions
$ curl -sI https://example.com/ | grep -iE 'cache-control|surrogate-control'
# common offender: a rendered block calling ::mergeCacheMaxAge(0) somewhere in code

# 4) Measure warm TTFB across 5 anonymous runs from a CDN POP
$ for i in 1 2 3 4 5; do \
    curl -o /dev/null -s -w 'ttfb=%{time_starttransfer}s\n' https://example.com/; \
  done
# expected on the after-state stack: 0.05-0.10s warm from a nearby POP