- Software and systems
- Database
53300
PostgreSQL 53300: too_many_connections
Evidence linked to this decision
View source: PostgreSQL 18 Appendix A: Error CodesRisk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
SQLSTATE 53300 (too_many_connections) means PostgreSQL has no normal connection slot available for the new session. Diagnose the named condition before retrying.
Safety first
Stop and check this first
- Do not terminate unknown sessions or raise max_connections blindly during an incident; both actions can worsen data loss or resource exhaustion.
Safe checks you can perform
- Measure who consumed the connection budget
What a technician must be able to justify
A technician is coming
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Measure who consumed the connection budget
Use an administrative path to group active and idle sessions by application_name, user, state and age; compare every pool maximum plus workers with max_connections and reserved slots. Stop leaks or reduce pool totals first. Raise max_connections only after memory, process and failover capacity review.
Evidence: PostgreSQL 18 Appendix A: Error Codes · PostgreSQL connection settings
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Virtual technician
Does 53300 still appear after these checks?
This guided flow uses the exact code and your answers to choose a test, an expected result and the next branch.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Software and systems
- Brand
- PostgreSQL
- Product type
- Database
Known code variants
- PostgreSQL 53300
- SQLSTATE 53300
- too_many_connections
What it means
PostgreSQL assigns 53300 to too_many_connections in Class 53 — Insufficient Resources. Applications should branch on the stable SQLSTATE and structured error fields, not localized message text.
Warnings and stop conditions
- Higheditorial warning
Do not terminate unknown sessions or raise max_connections blindly during an incident; both actions can worsen data loss or resource exhaustion.
Evidence: PostgreSQL 18 Appendix A: Error Codes · PostgreSQL connection settings
Symptoms and causes
Probable causes · in order
- Likely trigger in this requestCommon
Application pools, leaked or long-lived sessions, traffic spikes or background workers consumed the configured connection budget.
Evidence: PostgreSQL 18 Appendix A: Error Codes · PostgreSQL connection settings
Sources and technical references
- 1
PostgreSQL 18 Appendix A: Error Codes
PostgreSQL Global Development Group · 2026 · official_doc
- 2
PostgreSQL connection settings
PostgreSQL Global Development Group · 2026 · official_doc
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