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Web Performance Optimisation (WPO)7 min•Difficulty: Avanzado

[WPO-017] Find slow queries delaying dynamic pages

Use traces and EXPLAIN with authorised access; do not change indexes blindly.

Ingeniería de Rendimiento AnayilUpdated: 2026-10-10

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This answer covers “[WPO-017] Find slow queries delaying dynamic pages”. Read it with the summary and confirm that the symptom and service match what you are experiencing. Available options can vary by plan and account setup.

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L3 technical diagnosis

Performance / configurationSeverity: Medium; high if conversion or availability is affected

User symptoms

A dynamic page has high TTFB and latency grows with record volume.

Observed code or message

Query timeout / lock wait timeout; repeated slow queries

Likely root cause

Full scans, missing or unselective indexes, N+1 queries and locks increase CPU/I/O time. Adding indexes without reviewing writes and plans can degrade operations.

Likely-cause and resolution matrix

Follow a branch only when evidence supports it. A symptom may have more than one cause; do not change layers by guesswork.

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Prerequisites

Authorised access to the affected site, repository or service metrics.
A reproducible URL and timestamp; use staging for infrastructure changes.
A backup or rollback method for configuration and deployments.

Important warnings

Inspection commands do not authorise production changes. Do not run load tests or global purges without an approved plan.
Never store private responses in shared caches. Server changes in Anayil Panel depend on the controls available for the service and may require its administrator/provider.

Step-by-step walkthrough

1. Reproduce and narrow the issue

A dynamic page has high TTFB and latency grows with record volume. Correlate request ID with query digest, duration, examined rows and lock waits. Review EXPLAIN on a replica/staging or read-only session; redact personal data.

bash

EXPLAIN SELECT id, status FROM orders WHERE customer_id = 123 ORDER BY created_at DESC LIMIT 20;
# Run only with authorisation; on supported engines, EXPLAIN ANALYZE executes the query.

Expected output:

Query timeout / lock wait timeout; repeated slow queries

2. Apply the appropriate correction

Optimise the application query (including N+1), select only needed columns and review a composite index with the DBA based on filters/order and write cost. Schema changes require a migration, backup and rollback plan.

3. Verify the experience

Compare duration, examined rows and load for the equivalent query; confirm functionality with realistic data volume and no new locks.

Expected output:

The improvement is reproducible on the affected route and profile with no new functional errors.

Troubleshooting & Solutions

Query timeout / lock wait timeout; repeated slow queries

Root cause: Full scans, missing or unselective indexes, N+1 queries and locks increase CPU/I/O time. Adding indexes without reviewing writes and plans can degrade operations.

Resolution: Optimise the application query (including N+1), select only needed columns and review a composite index with the DBA based on filters/order and write cost. Schema changes require a migration, backup and rollback plan.

Rollback and recovery plan

Roll back only the changed directive, dependency or release using the recorded value. If 5xx errors, data exposure or session failures occur, have the operator disable the new rule and retain redacted logs for analysis.

Related runbooks in this category:

[WPO-001] Separate origin latency from browser delay7 min [WPO-002] Diagnose intermittent latency without mislabeling constant slowness7 min [WPO-003] Reduce redirect chains in the page-load path7 min

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