Performance issue on CosmosDB for MongoDB

Question

I am experiencing performance issue with CosmosDB for MongoDB (RU), when executing a query on a collection containing 300,000 documents. The query takes 43 seconds to execute on CosmosDB, whereas on my local MongoDB setup, it only takes 411 ms. Both env having the same data and same indexes + i have executed other queries also to evaluate and compare the performance and i am seeing significant performance difference. Additionally CosmosDB is on DEV environment so there is no traffic on the server.

What could be causing this significant performance difference ?

Answer 1

Hi Sanjay Mange •,

Welcome to Microsoft Q&A forum.

As I understand, you want to know performance difference between MongoDB and Azure Cosmos Mongo DB(RU).

Performance depends on multiple factors:

1). Whether DB is Provisioned or Serverless.

2). Check RUs allocated.

Choose RU-based if

• You're building new cloud-native MongoDB apps or refactoring existing apps for cloud-native benefits.
• Your workload has more point reads (fetching a single item by its _id and shard key value) and few long-running queries and complex aggregation pipeline operations.
• You want limitless horizontal scalability, instantaneous scale up, and granular throughput control.
• You're running mission-critical applications requiring industry-leading 99.999% availability.

You'd like a multitenant service that instantly allocates resources to your workload, aligning with storage and throughput requirements.

Throughput is based on Request Units (RUs).

RU charges depend on the selected model: provisioned throughput (standard or autoscale) or serverless.

Refer: https://learn.microsoft.com/en-us/azure/cosmos-db/mongodb/cosmos-db-vs-mongodb-atlas?source=recommendations#azure-cosmos-db-for-mongodb-vs-mongodb-atlas

Could you please check configuration of your DB and share details.

Thanks.