Cookbook recipe

Set up streaming replication from scratch

Applies to PostgreSQL 13–17 Last reviewed May 2026 Grounded in source

What This Is

A production experience capsule based on real incident patterns.

Why It Matters

Builds production judgment under pressure.

Next Step

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Estimated investigation4 min

Scenario

You need a hot standby for read scaling and failover. Streaming replication ships WAL to a replica in near real time. Diagnose it On the primary, confirm WAL level and a replication slot: SHOW wal_level; --…

Investigation Path

You need a hot standby for read scaling and failover. Streaming replication ships WAL to a replica in near real time.

Diagnose it

On the primary, confirm WAL level and a replication slot:

SHOW wal_level;   -- replica or logical
SELECT * FROM pg_create_physical_replication_slot('standby1');

Why it happens

A standby replays the primary’s WAL. A replication slot guarantees the primary keeps WAL the standby still needs, preventing the dreaded “requested WAL segment has already been removed”.

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Related & next steps

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Concepts on this page

Replication lag Replication
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