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Grokking the Product Architecture Interview

Discussion on Response Time

Explore methods to calculate API response times using both parallel and serial processing approaches. Understand how latency and processing affect GET and POST requests. Discover practical optimization strategies like caching, database tuning, and CDN use to enhance API performance and ensure real-time responsiveness in product architecture.

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Calculate response time using parallel processing

Let’s use the equation for response time with which we are already acquainted:

In parallel processing, the API gateway communicates with all the subservices simultaneously, as shown in the following illustration:

Parallel processing from API gateway to downstream services
Parallel processing from API gateway to downstream services

We’ll use the processing time to calculate the response time of an API. For that, recall the latency numbers we estimated in the latency lesson to measure the response time of GET and POST requests. Let’s populate the numbers in equation (1):

  • Response time for a GET request=331.42 ms+4 ms=335.42 ms= 331.42\ ms + 4\ ms = 335.42\ ms

  • Response time for a POST request=805.48 ms+4 ms=809.48 ms= 805.48\ ms + 4\ ms = 809.48\ ms

The response time is significantly reduced on subsequent requests when the base time is omitted after using a cached response:

  • Response time for a GET request =128.32 ms+4 ms=132.32 ms= 128.32\ ms + 4\ ms = 132.32\ ms ...