How to Connect to Amazon DocumentDB Using mongosh: Common Errors and Solutions

• Amazon DocumentDB is a MongoDB-compatible managed database, but it has some differences that can trip up developers trying to use modern MongoDB clients.
• Troubleshooting connection issues – Amazon DocumentDB is often necessary because connecting to Amazon DocumentDB may throw errors that can be confusing, especially because DocumentDB is MongoDB-compatible but not identical.

1.Wire Version Mismatch

“MongoServerSelectionError: Server at <cluster-endpoint> reports maximum wire version 6, but this version of the driver requires at least 8 (MongoDB 4.2)”

DocumentDB 3.5 (and 3.6) supports MongoDB wire version 6 (features roughly equivalent to MongoDB 3.6).

Modern clients (mongosh 2.x, Node.js driver 4.x, MongoDB shell 8.x) require wire version 8 or higher, which corresponds to MongoDB 4.2+.

The client attempts to use features the server does not support → connection rejected.

Solution is to:-

Use a compatible MongoDB shell or driver:

Mongo shell 4.0.x

Node.js MongoDB driver 3.x

Python pymongo 3.x (not 4.x)

Avoid mongosh 2.x for DocumentDB 3.5 clusters.

2. ECONNRESET (Connection Reset by Peer)

“MongoServerSelectionError: read ECONNRESET”

The server forcibly closes the connection during handshake. Common reasons:

Network/firewall or security group blocking traffic on port 27017

Wrong TLS/SSL configuration (invalid CA certificate, missing ssl=true)

Connection string missing required parameters (replicaSet=rs0, retryWrites=false)

Solution is to:-

Check network connectivity using,

telnet <cluster-endpoint> 27017

Use correct TLS CA:

–tlsCAFile /path/to/rds-combined-ca-bundle.pem

Ensure security groups allow your machine’s IP.

3 .Authentication / Unsupported Mechanism

“MongoServerError: Authentication failed / Unsupported mechanism SCRAM-SHA-256”

DocumentDB 3.5 supports SCRAM-SHA-1, but not SCRAM-SHA-256 or other advanced auth mechanisms.

Some clients default to SCRAM-SHA-256 (modern MongoDB shells/drivers).

Solution is to:-

Force authentication against the admin database:

authenticationDatabase admin

Ensure the client version supports SCRAM-SHA-1.

4 .Timeout / Server Selection Errors

“Server selection timed out after 30000 ms

connect ETIMEDOUT”

The client cannot find a suitable server for operations. 

The Possible reasons are;

• Using an instance endpoint instead of the cluster endpoint

• Network or firewall blocking the connection

• Replica set parameters missing or misconfigured

• Read preference conflicts

Solution is to :-

Use cluster endpoint, not individual instance endpoints.

Include correct replica set name:

replicaSet=rs0

Set read preference:

readPreference=secondaryPreferred

5 .TLS/SSL Handshake Failures

“MongoServerSelectionError: SSL handshake failed / certificate verify failed”

DocumentDB requires TLS/SSL connections.

Using an incorrect CA bundle or missing –ssl or –tlsCAFile flags causes handshake failure.

Solution is to:-

Download AWS CA bundle:

wget https://truststore.pki.rds.amazonaws.com/global-bundle.pem -O /root/global-bundle.pem

Use it in your connection:

--tlsCAFile /root/global-bundle.pem --ssl

Ensure the client supports TLS 1.2 (modern MongoDB shells do).

By following these best practices, you can reliably connect to DocumentDB, troubleshoot errors effectively.DocumentDB may not be a drop-in replacement for MongoDB, but with the right client configuration, it can integrate seamlessly into your applications.

Conclusion

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