Tuning MongoDB for Optimal Performance
Adam C. |


MongoDB, a widely used NoSQL database, offers flexibility and scalability for various applications. However, to ensure optimal performance, it's crucial to fine-tune your MongoDB deployment. This guide addresses common warnings and provides best practices to optimize your MongoDB setup.

Photo by Denisse Leon on Unsplash

MongoDB Startup Warnings

Upon connecting to MongoDB as admin using the mongosh shell, you might encounter startup warnings. Here's a sample:

The server generated these startup warnings when booting
2024-01-05T16:57:45.876+00:00: Using the XFS filesystem is strongly recommended with the WiredTiger storage engine. See http://dochub.mongodb.org/core/prodnotes-filesystem
2024-01-05T16:57:47.475+00:00: vm.max_map_count is too low

These warnings highlight two critical aspects:

Filesystem Recommendation:
MongoDB recommends using the XFS filesystem when employing the WiredTiger storage engine. XFS is known for its scalability and performance characteristics, making it an ideal choice for MongoDB. To address this, follow the steps outlined in the MongoDB documentation to switch to the XFS filesystem. (Note that XFS may not be available as an option for most VPS providers!)

MongoDB XFS Filesystem Documentation

vm.max_map_count Setting:
The warning about vm.max_map_count being too low indicates that the current setting might not be sufficient for MongoDB's requirements. This kernel parameter controls the maximum number of memory map areas a process can have. To resolve this, you can adjust the vm.max_map_count setting.

Tuning vm.max_map_count

Temporary Adjustment (Runtime):

sudo sysctl -w vm.max_map_count=<new_value>

Replace <new_value> with the desired new value, such as 262144.

Permanent Adjustment (Across Reboots):

1. Edit the /etc/sysctl.conf file:

sudo vim /etc/sysctl.conf

2. Add the following line:


3. Save and exit the text editor.

4. Apply the changes:

sudo sysctl -p

General MongoDB Tuning Tips


  • Ensure that your queries are well-indexed based on your application's usage patterns.
  • Regularly analyze and optimize indexes for improved query performance.

Memory Configuration:

  • Allocate sufficient RAM to MongoDB to minimize disk I/O.
  • Adjust the wiredTigerCacheSizeGB configuration for WiredTiger to optimize memory usage.

Storage Engine Consideration:

  • Evaluate the storage engine based on your workload. WiredTiger is the default and recommended for most use cases.

Connection Pooling:

  • Configure connection pooling settings to efficiently manage client connections.

Monitoring and Profiling:

  • Regularly monitor database metrics using tools like MongoDB Cloud Manager or similar solutions.
  • Enable the MongoDB profiler to identify slow-running queries for optimization.


  • Consider sharding for horizontal scaling if your dataset grows beyond the capacity of a single server.


Tuning MongoDB involves a combination of adjusting system parameters, optimizing queries, and configuring MongoDB settings to match your application's requirements. Regular monitoring and performance analysis are key to identifying potential bottlenecks and ensuring continued optimal performance. Refer to the MongoDB documentation and community resources for detailed guidance on specific topics.