[kiechu]

The site is served via AWS CloudFront. It is SPA app hosted on S3. The API is on Heroku. No mem-cache anywhere. To search we use ElasticSearch hosted on AWS. We bump up the specs to speed it up but that was not the core problem.

I suspect Heroku Postgres DB. We didn't used some Hobby version and I think it is the real bottle neck + some unnecessary middleware for the API that also requires DB.

[gammateam]

maybe a mem-cache then?

DB's have limited connections and are often billed as such, the mem-cache might help if there are any repeatable things. It might not be useful for your solution though since everyone searches for their own things all the time.

[kiechu]

Increasing DB plan did the job.