Error
Error Code:
61
MongoDB Error 61: Missing Shard Key Definition
Description
This error indicates that MongoDB cannot find a defined shard key for a collection during an operation within a sharded cluster. It typically occurs when a collection is not properly sharded or the shard key is referenced incorrectly.
Error Message
Shard Key Not Found
Known Causes
3 known causesCollection Not Sharded
The target collection has not been properly sharded or its shard key was not defined using `sh.shardCollection()`.
Incorrect Collection Reference
The operation is referencing a non-existent or misspelled collection name within the sharded cluster.
Shard Key Mismatch
The operation attempts to use a shard key that doesn't match the one defined for the collection, or the key is malformed.
Solutions
3 solutions available1. Include Shard Key in Query medium
Add shard key field to query filter
1
Check shard key
sh.status()2
Include shard key in query
// If sharded by user_id:
db.orders.find({ user_id: "123", status: "pending" })3
For updates, include shard key
db.orders.updateOne(
{ _id: ObjectId("..."), user_id: "123" }, // Include shard key
{ $set: { status: "complete" } }
);2. Use Multi Update for Scatter-Gather easy
When shard key unknown, use multi:true
1
Use updateMany for broadcast
db.orders.updateMany(
{ status: "pending" },
{ $set: { status: "cancelled" } }
);3. Verify Document Has Shard Key easy
Ensure document contains shard key field
1
Check document structure
db.orders.findOne()2
Insert must include shard key
// If shard key is user_id:
db.orders.insertOne({
user_id: "123", // Required!
product: "item",
total: 99.99
});