What makes the web app or mobile app fast or slow?

Martin Sults
CrewNew.com
Published in
3 min readNov 6, 2022

It doesn’t matter if it is a website, e-shop, web app, mobile app or desktop app — they all could be annoyingly slow. But it doesn’t have to be like that. They could also be super fast and when you click somewhere, the new view will load instantly or with a slight (maybe 200–300ms) transactional animation. Fade/zoom/slide/etc. It will be then a SPA (single-page-application) and my colleague Kaspar has written about it here>>

So, let’s learn what are the factors that affect the speed:

Front-end (FE) technologies

FE is the picture, text, video, and everything you see with your eyes. How the data will be displayed to you visually — that’s what the FE does. The back-end(BE) deals the magic in the background and provides the correct data to the FE via API in modern apps and then the FE displays it.

If we use the old-school jQuery in the FE then each new view will be loading a new web page URL and things aren’t that fast vs using some modern FE stack like Svelte (best), React (most popular), Vue (open-source React competitor) or Angular (the first one but not so popular any more). In the modern FE stack only when you arrive at the website the very first time the loading will be done and during that, we could show some initial content already while the data loads in the background. We can also program it in a way that all the third-party scripts (like Google Analytics, Facebook pixel, etc. etc.) will be loaded a bit later when we have already something to show to the visitor. In that way, we can generate the perfect user experience (UX). Once the initial loading is done we can already pre-render the data that we expect the visitor to click next and provide instant loading.

Instant loading and cool tiny animations are great UX andhave a cool and modern vibe. And Google knows it so it will also rank you higher in the search results which means huge economic profit for you. No need to pay expensive PPC for AdWords.

Super fast app = super cool app😎

Back-end technology

BE dictates how quickly the FE gets the data before it even can start rendering it. If you use some old-school massive back-end stack (PHP Zend, Magento, WordPress, etc.), it might take seconds before the FE even gets the data. For example, for Magento, less than 8GB RAM for the server is guaranteed mega-super-slow.

But if you use some well-cached modern API solution like Hasura, Directus, and/or NodeJS then the speed difference could be tens of times in the same machine.

Data amount in BE and data complexity

How large is the database (DB) and how “deep” are the queries in the database? For example, if you have 50m products and hundreds of re-sellers who have thousands of shops that have thousands of sales agents etc then obviously it will be slower compared to some small e-commerce solution. Also, is the database just enough normalized and optimised?

The server’s computing power

How much RAM and CPU does the server have? If we put our badly written solution to the server with an 8-core Ryzen processor and 32GB RAM then it will be still reasonably fast but you’ll be paying a huge monthly bill, too! Also, it is important how fast the internet connection it has and how far is the server from its users.

Need a fast app or maybe just some consultation? Let’s chat: wa.me/447588699948 or martin.sults@crnw.uk

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