Case Study: Enhancing Mobile App Performance for a Supermarket Chain

How resolving a seemingly simple technical issue in a mobile app for a supermarket uncovered deeper challenges for their business.


A number of years ago, soon after joining a leading agency, I was tasked with addressing performance issues they were having in a mobile application for a well-known supermarket retailer.

The iOS app was underperforming, plagued by frequent crashes, and slipping in the App Store rankings. This situation was not only a technical challenge but also a strategic concern for the client, especially as they were gearing up to introduce a significant new feature: providing in-app alcohol purchases.


The app was experiencing over 1,500 crashes per day, which was severely negatively impacting user engagement metrics such as time spent in the app, product views per session, and add-to-basket conversions which were plummeting costing the company hundreds of thousands of Pounds.

These technical issues had caused the app’s ranking to plummet from 35th to 85th in the App Store “Shopping” category over a six-month period. My objective was clear: I had to stop the bleeding. Stabilize the app, re-gain user trust, and prepare the platform for the new feature rollout.


  1. Crash Analysis and Immediate Fixes:
    • Identified and isolated the source of frequent crashes — dead code that mishandled data persistence.
    • Implemented a hotfix to bypass the problematic code within three days, followed by a comprehensive update that removed the dead code entirely.
  2. Codebase and Performance Enhancements:
    • Overhauled the entire codebase to utilize the latest version of Swift, ensuring more robust and future-proof operations.
    • Made subtle yet impactful UI enhancements to speed up the Product Detail screen load times.
  3. App Store Performance Recovery:
    • Dramatically reduced crash frequency from 1,500 to just 7 per day*. For hundreds of thousands of people, the app went from crashing daily to being rock solid.
    • Enhanced user engagement metrics, with significant increases in time spent in-app and product views per session, leading to improved conversion rates.
  4. Business Strategy Realignment:
    • Post-improvement, the mobile app began to outperform the client’s website in user engagement and conversions.
    • However, the enhanced efficiency of the mobile app surfaced a strategic discrepancy with the client’s business model, which relies on low headline prices to drive store footfall and upsell customers on impulse purchases.


The technical improvements led to the app’s rise back up the charts to beat its original position in the App Store, surpassing competitors like Lidl and even high-end retailers like John Lewis in certain metrics. However, the project also highlighted a critical insight: improving the mobile app’s efficiency paradoxically undermined the client’s traditional business model. The client chose to scale back the app’s functionality, reducing its prominence to preserve the profitability of in-store upsells.


This project exemplified the complexity of aligning technical solutions with business strategy. It demonstrated that sometimes the apparent problem might not be the one that truly needs solving. Through this initiative, I showcased not only my capability to lead and execute on the technical front but also my strategic acumen in recognizing and adapting to the broader business implications of technological enhancements.

* Over the following weeks on the project, I’d hunt down the remaining crashes, and they turned out to be a caused by a certain enthusiastic customer trying to run the app on an unsupported, much older device! I suggested to the client that it might be cheaper to gift them a new device than trying to support them. I don’t know if they ever got a new iPhone, but I somehow doubt it!