MongoDb slow performance

Posted on June 9, 2024

Hi, I am trying to move my infrastructure from different cloud provider and got stuck on MongoDB performance in Digital Ocean. All my queries take two times more execution time than it should be compare to previous provider and even localhost. I tested it on the same data, no indexes.

I used .explain("executionStats") command to get execution times. The results:

Digital Ocean:

"executionStats": {
  "executionSuccess": true,
  "nReturned": 12,
  "executionTimeMillis": 609,
  "totalKeysExamined": 0,
  "totalDocsExamined": 333969,

Previous provider:

"executionStats": {
  "executionSuccess": true,
  "nReturned": 12,
  "executionTimeMillis": 256,
  "totalKeysExamined": 0,
  "totalDocsExamined": 333969,

Localhost:

`"executionStats": {
  "executionSuccess": true,
  "nReturned": 12,
  "executionTimeMillis": 221,
  "totalKeysExamined": 0,
  "totalDocsExamined": 333969`,

I run these tests multiple times, tried different queries, but DO is always significantly slower. I tried to scale up DO more, but it didn’t help. I use managed MongoDB 4 GB RAM / 2vCPU / 56 GB Disk in Frankfurt. I had similar setup with previous provider.

Any help appreciate it, thank you.

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4a14ba3a148542cab1814465d54cbf

June 9, 2024

Update: I tried to test self hosted Mongo on basic Droplet and execution time is solid. Looks like the issue is in managed MongoDB.

Bobby

June 9, 2024

Hey!

It sounds like that this could be just network latency, if you were running the statements from the server itself it would explain why you are seeing the same behavior on your localhost and on the Droplet that you’ve just created.

However, if you are running the statements from your local computer to the remote managed database, it would explain the few hundred milliseconds difference.

Basically, the physical distance between your MongoDB server in DigitalOcean’s data center and your current location might be contributing to increased response times. You could try to spin up a Droplet where you would be running your application on, and measure the execution time when running the statements from the Droplet to the Managed Database that are in the same region.

Let me know how it goes!

- Bobby