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M
124
Easy Fix
MongoDB · Database Server & Atlas
MongoDB server reported: RPC Protocol Negotiation Failed.
Quick Answer
Error code 124 on your MongoDB Database Server & Atlas means: MongoDB server reported: RPC Protocol Negotiation Failed.. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
MONGO-ATLAS-DEDICATEDMONGO-ATLAS-SERVERLESSMONGO-COMM-6.0MONGO-COMM-7.0MONGO-COMM-8.0MONGO-ENT-6.0MONGO-ENT-7.0MONGO-ENT-8.0
Likely Causes
  1. MongoDB returned code 124 (RPCProtocolNegotiationFailed) while processing this request path.
  2. Object identifiers, namespaces, or index metadata did not match current server state.
  3. Client and server protocol expectations diverged for this operation.
How to Fix It
1
Review logs/telemetry for code 124 (RPCProtocolNegotiationFailed) and capture the exact command and parameters that triggered it.
2
Validate request schema, field types, and identifiers against current server rules.
3
Reproduce with a minimal payload to isolate which attribute is rejected.
4
Add client-side guards and contract tests so this validation pattern is blocked pre-deploy.
5
Add monitoring for recurring RPCProtocolNegotiationFailed events so future incidents are detected and triaged faster.
Pro Tip
This is a common issue that most users can resolve without specialized tools. Try the first step before moving on to more complex solutions.
Related Error Codes
12456
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