App store ratings are brutal and honest. “Works great but slow to load” translates directly into a two-star review and an uninstall. Performance is not a nice-to-have. It is a product requirement.
Here are the most common performance problems we see in mobile codebases — and how to fix them.
Blocking the main thread. Any operation that takes more than 16ms on the main thread causes a dropped frame. Database reads, network requests, image decoding — all of these belong on background threads. If you are not explicitly managing your thread pool, you are probably blocking.
Over-fetching data. Most mobile apps request far more data than they display. A paginated list of 20 items should not require fetching 500 rows from the server. Implement pagination, lazy loading, and request scoping at the API layer.
Unoptimised images. Images are the single largest contributor to memory pressure in most mobile apps. Use WebP, size images to their display dimensions (not full resolution), and cache aggressively. A 4MB hero image on a 360px-wide screen is a product bug, not a design decision.
No offline strategy. Users lose connectivity. If your app crashes or becomes completely unusable without a network connection, you are building a bad product for most of the world. Implement optimistic UI, local caching, and graceful degradation.
