First request for Google Cloud NodeJs API taking more time than subsequent requests

Question

I have a nodejs based aplication running as a Google App Engine application. It accesses the database using node-postgres module. I have noticed the following:

• The first request that I am making from my machine (using postman) is taking longer (around 800 ms- 1.5 seconds). However, the subsequent requests that I am making are taking much lesser time (around 200 ms - 350 ms). I am unable to pinpoint the exact reason for this happening. It could be due to the following reasons:
• A new connection is initiated the first time I make a request to the server.
• There is some issue with the database fetching using node-postgres (But since the problem occurs only at the first instance, this is more unlikely).

I am worried about this issue because logs are showing me that almost 20% of my requests are taking around 2 seconds. When I viewed the logs for some of the time taking requests, they seemed to be instantiating a new process which was leading to the longer wait time.

What can I do to investigate further and resolve this issue?

Answer 1

Your first request take more time than the others because App Engine standard has a startup time for a new instance. This time is really short, but there is. You need to add the time to set up the connection to the database. This is why you have a longer response time for the first request.

To understand better the app engine start time you can read the Best practices for App Engine startup time doc (little bit old but I think really clear). And to perform profiling for your app engine application you can read in this Medium public blog.

After this, you can set up a Stackriver dashboard to understand if your 20% of slow requests are due to the start of a new app engine instance.