Help with intermittent network issue

My rails app is deployed to SIN, it connects to an RDS, also in Singapore. I have recently experienced intermittent network issues between the app and the database. I checked all metrics, everything looks fine, database memory and CPU usage is consistently low, app memory and CPU are also low. I ssh-ed to the app and try performing database query, everything is fine as well. There was an instance where most of the requests timed out, and I had to redeploy the app itself to recycle the instance, then it resolved but still the intermittent timeout error to database.

Is there any pointer to debug the issue?