@Parth_Narang Welcome to the community!
I suspect the vast majority of that 350 milliseconds is the actual marshalling and construction of the response json document.
And is that 350 milliseconds measured from where?
You can run it in the profiler and see how long it's actually taking.
But 10,000 documents, even though they're small is going to take time to marshall and transmit.
Not that this matters really but that's a 100km not 10 km
"distance": 100000
Also if it the actual query you could try
"distance_type" : "plane"
To speed it up
Curious what the took says
And also curious How you arrived at 200 milliseconds should be good for the 10,000 documents. Did you get that performance before?
Do you need all 10,000 documents in a single response or could you page through them?
Also, 7.9.1 is very old. There's been a number of performance improvements we're all the way up at 8.4 with. There has been significant underlying changes to the lucene engine. I would also try upgrading if you can.
And as I'm sure Christian was getting to EBS is not the best storage for high IO Not that it won't work, but it's certainly not the lowest latency option.. on the other hand, if you keep hitting those indices and there's not much else going on, most of those indices could be in RAM... But if it's a busy cluster that won't be the case.
Hard to say...