MongoDB Slow Queries

I am performing tests with mongodb version 4.2.6. The queries take 100-200ms.

All queries are indexed and indexes being used. Enough memory is allocated to fit memory in indexes. Also, a good part of the working set fits in memory. However, the queries take 100-200ms which is quite high.

Based on mongodb logs, here is what it’s spending it’s most of the time:

storage:{ data: { bytesRead: 133612, timeReadingMicros: 174431 } } op_msg 174ms

How can be this time optimized to reduced query time?

Total memory available: 32GB
Index Size: 28.39GB
Frequently accessed data size: 1-2GB
Total data size: 424.37GB
Data size on disk with compression: 107.10GB
WiredTiger mem allocation: Default - 50% (RAM -1) GB

Thanks!