How do you plan a mobile app backend and API?

1. Start with data and responsibilities

Map who creates data, who can change it and what is shared by the web and mobile apps. Separate interface state from data for which the server is the source of truth. Decide how the app detects conflicts when two people change the same record.

The public overview of the ZEiT project shows a store, admin panel and Flutter app using a Laravel API. This requires consistent backend rules; repeating validation in every interface is not enough.

2. Define the REST API contract and error handling

Define resources, operations, data formats, pagination and dates. Explain optional fields and the difference between a missing value and an empty list. The contract should be clear to both teams and testable, regardless of the documentation format.

Validation errors, missing authentication, insufficient permissions and unavailable integrations require different app responses. Define HTTP statuses, stable error codes and a request identifier for diagnostics. Human-readable messages can change or be translated; clients should not drive logic from their exact wording.

3. Separate authentication from permissions

A token or session identifies a user but does not determine which data they can access. Every resource operation should check server-side permissions. Hiding a button or identifier in the app is not a security measure.

Plan token expiry and revocation, single-device sign-out and responses to lost account access. Choose session or token mechanisms suitable for the client. Add request limits and security event logging without storing passwords or full tokens in logs.

4. Account for poor connectivity and retries

A phone may lose its connection after the server saves data but before it receives the response. A timeout alone does not mean the operation failed. For important writes, plan an operation identifier and safe retry so clients do not create duplicates.

For uploads, define size limits, allowed types, file permissions and completion confirmation. Longer processing can run in a queue while the API returns job status. Plan removal of incomplete files and error handling after interrupted transfers.

5. Separate queues, push and real-time communication

A queue lets work run outside an HTTP request, but requires monitoring delays, retries and failed jobs. Define which operations can be repeated, how duplicates are detected and when intervention is needed instead of another attempt.

Push notifies a device, while WebSockets provide live communication with a connected client. Neither should be the sole store of important state. After reconnecting, the app should be able to fetch current data from the API.

In Spontan, the publicly described stack includes Laravel Reverb, Redis queues and a Flutter app. This illustrates separating chat communication from other backend operations.

6. Plan caching and integration failures

Caching can reduce read costs, but first define acceptable staleness and invalidation. Keys must account for access context; one user's data must not appear in another user's response.

Any external integration can slow down or stop responding. Define timeouts, retries, webhook handling and the state shown to users. When part of a process succeeds and part fails, you need reconciliation rather than guessing whether to run everything again.

7. Stay compatible with older app versions

A new store release does not reach every user immediately. Avoid removing fields or changing their meaning without a migration plan. An API version number organises communication but does not itself guarantee compatibility. Test responses with client versions still in use.

Plan deployment order, the coexistence period and conditions for ending support for older clients. Monitor errors, response times and queue backlogs. Do not promise safe rollback until you know how newly written data behaves with restored older code.

What should exist before implementation?

Start with a shared data model, operations and permissions, example responses, error scenarios, and an integration and deployment plan. Details evolve with the product, but clarify data ownership and version compatibility early.

These decisions connect backend, API and integration services with the requirements of a Flutter mobile app.

Documentation for your next steps

Use installation instructions that match the versions in your project. The sources below cover these topics in more detail.

• Laravel — queues and retries
• OWASP — API security