Question: How can you improve MongoDB inserts per second?

Answer

Improving the number of inserts per second in MongoDB involves optimizing both the database setup and the application code that interacts with it. Here are several strategies to enhance insert performance:

1. Use Bulk Operations

Leverage bulk insert operations instead of inserting documents one at a time. This reduces network overhead and increases throughput. Example:

db.collection.insertMany([
  { item: 'item1', qty: 10 },
  { item: 'item2', qty: 20 },
  // more documents...
]);

2. Write Concern

Adjust the write concern level according to your needs. A lower write concern (e.g., {w: 0}) can increase insert speed by not waiting for the operation to be confirmed, but at the cost of durability.

db.collection.insertOne(
  { item: 'item3', qty: 30 },
  { writeConcern: { w: 0 } }
);

3. Indexed Fields

Ensure that fields which are frequently queried are indexed, but also be careful not to over-index as each additional index can slow down insert operations. Only maintain necessary indexes.

4. Sharding

For very high throughputs, consider sharding your data across multiple servers. This distributes the load and allows for horizontal scalability. Proper shard key selection is crucial for evenly distributing data.

5. Hardware Considerations

• RAM: Ensure there is enough RAM to hold your working set to avoid disk I/O bottlenecks.
• Disk Type: Use SSDs for faster write operations compared to HDDs.
• Network: Ensure your network bandwidth is not a bottleneck, especially when using sharded clusters or when the application is physically distant from the database server.

6. Document Design

Keep document size in mind; smaller documents mean more can be processed at a time. Also, structure your documents to minimize modifications to large arrays or deeply nested structures, which can be costly.

7. Connection Pooling

Use connection pooling to reduce the overhead of establishing connections to the database. Most MongoDB drivers manage this automatically, but it's important to configure the pool size according to your application's needs.

Conclusion

Optimizing MongoDB for higher insert rates involves a combination of application-level changes and database configuration adjustments. Start with bulk operations and appropriate write concerns, and then consider your indexing strategy, sharding, and hardware specifications. Remember to also pay attention to your document design and connection management for the best overall performance.