Performance Improvement and Null Safety Enabling for Grocery Delivery Mobile App

Flutter version update and code adjustments for a delivery app
Customer location
  • Germany Germany
Project duration
  • 2 weeks

Client and Business Goals

Our client, a Germany-based startup that provides on-demand grocery delivery services from the local markets in several German cities.

The client’s business is based on fast and sustainable goods delivery. To ensure the high quality of provided service, they developed a mobile application, allowing their clientele to order food quickly and safely, which was especially important during the pandemic.

The application was built with Flutter and after a few years of use, they faced some performance problems due to the outdated technology version. In addition, they needed to implement a null safety function to make the application compatible with later Flutter versions.

To make the amendments in the application code, the client was looking for a reliable partner with a proven track record of Flutter app development, and our team was chosen as a contractor for the project with no hesitation.


When we started working on the project, there was an issue with backend responses. The problem was in the error of field labeling (whether it was obligatory or not). Obligatory fields were labeled as non-nullable, and the backend sent them back as nullable, which caused errors.

To fix the issue, we went through the fields to add the logic of nullable variables and refresh the logic assignment of the fields for error-free backend functioning.


We migrated the application to the latest version of Flutter and made some code adjustments due to modifications that had occurred in the technology. To make the system compatible with later Flutter versions we enabled a null safety function and added nullable logic for backend models to make the app easy to update.


  • Flutter


We offer a set of migration services: from migration to microservices, to the cloud, and to higher software versions migration. This project illustrates the latter. The client’s application was migrated to the latest Flutter version, and our effort ensured flawless application functioning and outstanding customer experience.

A huge number of people use on-demand delivery apps on a regular basis. Statista forecasts that the revenue of this market is expected to be $401.3 billion in 2025, with over 2.63 billion users. If your business relies on outdated software, we encourage you to pay attention to its modernization.

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