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5 Ways to Make a Slow App Feel Fast

You know the feeling. A slow app opens, the button looks ready, and then nothing happens for a second too long. You tap again, just to check. It is not broken. It still does the job. It just makes every small step feel like waiting. That pause adds up, and after a few of those pauses, people stop trusting the app, even when the work behind it is sound. Speed, in this case, is not about showing off. It is about keeping the app out of the reader’s way.

In short: A slow-feeling app is often doing too much work on each tap, or asking for the same data again and again. Five simple changes help: batch database calls, add an index, cache popular data, load images only when needed, and update the screen at once. Used together, they cut needless waiting without changing what the app does.

In this guide

1. Fix N+1 queries so a list needs fewer database calls

When a feed shows twenty posts, the app may first ask the database for the list. Then it asks again for each post’s author, one by one. That is twenty extra calls for one screen, and each call takes a little time. The work is small on its own, but the total wait grows with every item on the list. Batching changes the pattern: the app collects the authors it needs and fetches them together, so the list and its authors arrive in far fewer calls.

Everyday example: Picture a feed list with ten items. Without batching, the app may make eleven trips to the database: one for the list, then one for each author. With batching, it can make two trips instead: one for the list and one for the authors together.

Try this first: Ask your developer to check the slowest list screen and fix the N+1 queries on that screen before touching anything else.

2. Add a database index so lookups jump to the answer

Without an index, a database often has to scan row after row until it finds the record it needs. That is fine for a tiny table, but it gets slower as the table grows. An index works like a sorted list of pointers: it tells the database where to look, based on the field you search by. Add an index on a field people search by often, such as email, and the database can jump straight to the matching record instead of reading the whole table.

Everyday example: A login lookup is a clear case. Every sign-in searches by email, so an index on email keeps that search short, even when the user table has grown large.

Try this first: Put an index on the one field your busiest lookup searches by, then test that lookup before you add more indexes.

3. Cache hot data with Redis so repeat visits skip the database

Some data gets asked for again and again: a popular page, a top list, or a setting that rarely changes. Fetching it from the database on disk every time repeats the same work. A cache such as Redis keeps a copy in fast memory. The first request still comes from the database. The next request finds the copy in memory, which is a cache hit, and the page can be served without another slow database trip.

Everyday example: Take a popular page that thousands of readers open. The first reader triggers the database query, and later readers get the cached copy until it needs refreshing.

Try this first: Cache one popular, slow-changing page or list, and set a clear refresh rule so readers never see stale data for long.

4. Lazy-load images so the first screen paints sooner

A photo page can be heavy before anyone scrolls. If the app loads every image at once, the first screen has to wait behind images the reader may never reach. Lazy loading changes the order: it loads only the images on screen first, and loads the rest as the reader scrolls down. The page still has all its pictures. It just stops making the first view pay for the whole page.

Everyday example: On a long photo page, the top pictures load right away, while pictures further down wait quietly until they are close to the screen.

Try this first: Lazy-load images below the first screen, and keep the top image loading right away.

5. Use optimistic UI so a tap feels instant

Most apps wait for the server before they change the screen. The user taps like, and the button stays still until the server answers. That wait feels long, even when it is short. Optimistic UI flips the order: it updates the button or screen at once, as if the tap already worked, and then confirms the change in the background. If the server later says no, the app can undo the change and explain why. This is the step most builders skip, yet it shapes how fast an app feels.

Everyday example: A like or save button is the best test. Tap it, and it should fill in at once. The app can save that choice in the background while you keep reading.

Try this first: Make one common tap, such as like or save, update instantly, and add a simple fallback if the server rejects it.

How to pick which one to try first

Start with the screen that frustrates people most, then match the symptom to the fix. If a list gets slower as it grows, look at N+1 queries first. If one lookup gets slower as the table grows, an index is the likely fix. If the same page is opened again and again, caching is worth trying. If the first screen is heavy with photos, lazy loading will help most. If the data loads well but every tap still feels laggy, try optimistic UI.

Work on one change at a time. That way, when the app feels better, you know which change made the difference, and when something breaks, you know where to look.

Common mistakes to avoid

  • Adding indexes everywhere. Extra indexes can slow down writes, so add the ones your busiest lookups need and test them.
  • Caching everything without a refresh rule. Readers may then see old data long after it has changed.
  • Lazy-loading the top image. The first picture should load right away, or the first screen will look empty.
  • Using optimistic UI without a fallback. If the server rejects a tap, the screen must undo the change and say so plainly.
  • Changing all five techniques at once. You will not know which one helped, or which one caused a new problem.

Quick check before you finish

  • Have you found the slowest screen, not just the screen you guessed was slow?
  • Did you try one change at a time and test it before going live?
  • If you added an index or a cache, did you test it with realistic data?
  • Does the top image still load right away, with only lower images lazy-loaded?
  • If you used optimistic UI, is there a clear fallback when the server says no?
  • Is your cache refresh rule written down, so stale data does not linger?

Final thoughts

A fast-feeling app is rarely the result of one big rebuild. It usually comes from removing small waits that repeat on every screen: extra database calls, a lookup with no index, the same data fetched again, images loaded too early, and a button that waits for permission to change. Fix the wait that bothers people most, test it well, and then move to the next one.

Please note: Performance results vary by app and database size, and indexes and caching should be tested before going live. No single change will speed up every app by the same amount, so treat each of these five techniques as a starting point to test, not a promised result.

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