How to calculate database connection pool size?

Question

Let's say I expect about 100 requests per second, each request should take from 1 to 3 seconds (in an ideal world).

Create a pool of 300 connections? Or something a little higher to offset potential spikes?

Answer 1

It depends on the distribution of inbound events. Queuing theory can give you a formula (for a given distribution) how many connections you need so that the probability of failure (without a free connection in your case) will be no more than a certain percentage.

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