Performance Checklist

Checklist for a better web application performance

Performance is crucial in today's web applications. A slow app feels buggy to the users and makes them flee it. Although performance is such an important topic, there are so many optimization vectors that it's easy to forget some of them. The intent of this checklist is to gather performance practices to apply when developing a web application.

While we apply these practices, we should always keep the following rules in mind:

  • Don't optimize too early

  • Don't let performance ruin productivity

  • Always check an optimization is efficient by measuring performance before and after it

Objectives

Frontend

Optimize images

Images represent in average ~60% of a page's weight, thus it's an important part to optimize.

Reduce code size

Reduce number of requests

Prepare next requests

We can use prefetching to prepare the browser to next requests and make them faster or even instant. This article is a few old but explains well the following techniques.

Optimize time to rendering

Ideally the critical code should fit in 14KB in order to be server in the first TCP roundtrip (why 14KB?). These techniques help to achieve this goal.

Optimize fonts

Make animations smooth

User perceived performance

User-perceived performance is often disregarded but can be more important than actual performance. These techniques allow us to improve it.

Backend

General

  • Provide batch queries/transactions instead of making the client send multiple requests

  • Identify & optimize slow resources

  • Parallelize slow tasks

  • Use relevant data structures

  • Don't overuse serialization

  • Generate static content when deploying so that it will be computed only once

  • If possible, use jemalloc to improve memory allocation

Cache

Donโ€™t loose time with non-urgent tasks

Donโ€™t lose time with errors

Database

Network & Infrastructure

Measuring

Miscellaneous

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