As much as I would love to say that investing in speed should start from the first day, speed is not the highest ROI thing which should be worrying about when you are still looking for a product-market fit. The answer to this question depends on what kind of product you are looking to build and what is your user base. Some reasons you should consider investing in speed right from the get go includes:
- Your users start complaining about speed. If you start getting bug reports from your website saying that it is not loading fast, then it is a pretty straightforward sign.
- You are expanding your customer base from the urban centers of developed countries to the whole world. Most users in the world do not have ultra-fast internet connections to work with, and as developers in Silicon Valley, its difficult to build for empathy for how users with slow internet connections experience your app.
- You have a lot of users on mobile phones. In a talk in Google I/O 2016, Ilya Grigorik makes a compelling point that speed and resilience matter a lot on mobile even if you think your users are all on 4G LTE connections. Even in urban centers people are not only 4G LTE Speed all the time, as they frequently lose connections whenever they go into a subway or elevator. On the other hand people in rural areas go on 2G speed and rarely lose connection as they have little to none interference. Build for speed if you want the users to have a good experience.
- You are paying a lot in server costs. Often this means that you are searching and fetching too much data, or doing too much work that is unnecessary or can be optimized.