neon-postgres-egress-optimizer

Postgres Egress Optimizer

Guide the user through diagnosing and fixing application-side query patterns that cause excessive data transfer (egress) from their Postgres database. Most high egress bills come from the application fetching more data than it uses.

Step 1: Diagnose

Identify which queries transfer the most data. The primary tool is the pg_stat_statements extension.

Check if pg_stat_statements is available

SELECT 1 FROM pg_stat_statements LIMIT 1;

If this errors, the extension needs to be created:

CREATE EXTENSION IF NOT EXISTS pg_stat_statements;

On Neon, it is available by default but may need this CREATE EXTENSION step.

Handle empty stats

Stats are cleared when a Neon compute scales to zero and restarts. If the stats are empty or the compute recently woke up:

1. Reset the stats to start a clean measurement window: SELECT pg_stat_statements_reset();
2. Let the application run under representative traffic for at least an hour.
3. Return and run the diagnostic queries below.

If the user has stats from a production database, use those. If they have no access to production stats, proceed to Step 2 and analyze the codebase directly — code-level patterns are often sufficient to identify the worst offenders.

Diagnostic queries

Run these to identify the top egress contributors. Focus on queries that return many rows, return wide rows (JSONB, TEXT, BYTEA columns), or are called very frequently.

Queries returning the most total rows:

SELECT query, calls, rows AS total_rows, rows / calls AS avg_rows_per_call
FROM pg_stat_statements
WHERE calls > 0
ORDER BY rows DESC
LIMIT 10;

Queries returning the most rows per execution (poorly scoped SELECTs, missing pagination):

SELECT query, calls, rows AS total_rows, rows / calls AS avg_rows_per_call
FROM pg_stat_statements
WHERE calls > 0
ORDER BY avg_rows_per_call DESC
LIMIT 10;

Most frequently called queries (candidates for caching):