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Description

Error 50, 'Max Time M S Expired', indicates that a MongoDB operation, such as a query or aggregation, failed to complete within its allotted `maxTimeMS` execution limit. This error occurs when the specified time constraint is exceeded, typically due to long-running operations, inefficient query plans, or performance bottlenecks on the server.

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Error Message

Max Time M S Expired

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Known Causes

4 known causes

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Inefficient Query Execution

The MongoDB query or aggregation pipeline is not optimized, requiring excessive time to process the requested data.

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Resource Constraints

The MongoDB server lacks sufficient CPU, memory, or disk I/O to execute the operation efficiently within the given time.

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Large Data Scan or Missing Indexes

The operation needs to scan a vast number of documents or lacks appropriate indexes, leading to slow data retrieval.

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Aggressive maxTimeMS Setting

The `maxTimeMS` value was set too low for the expected complexity and volume of the operation, causing premature timeouts.

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Solutions

4 solutions available

1. Add Index for Query medium

Create index to speed up query

1

Identify slow query fields

db.collection.find({ field: value }).explain("executionStats")

2

Create index

db.collection.createIndex({ field: 1 })

3

Create compound index for multiple fields

db.collection.createIndex({ field1: 1, field2: -1 })

2. Increase maxTimeMS easy

Allow more time for the operation

1

Set timeout on query

db.collection.find({ field: value }).maxTimeMS(60000)  // 60 seconds

2

Set in aggregation

db.collection.aggregate([...], { maxTimeMS: 60000 })

3. Optimize Query medium

Reduce query scope

1

Limit results

db.collection.find({ field: value }).limit(100)

2

Project only needed fields

db.collection.find({ field: value }, { name: 1, email: 1 })

3

Add more selective filter

// Add date range to reduce scanned documents
db.logs.find({
  created: { $gte: ISODate("2024-01-01") },
  level: "error"
})

4. Check for Collection Scans medium

Avoid scanning entire collection

1

Check query execution plan

db.collection.find({ field: value }).explain("executionStats")
// Look for "COLLSCAN" which indicates no index used

2

Use hint to force index

db.collection.find({ field: value }).hint({ field: 1 })

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Related Errors

5 related errors

MongoDB Error 50: Operation Exceeded Time Limit