Implementation
Build a web application interface
A web application receives up to five usable views for one defined workflow, connected to existing APIs.
Implementation / Backend development & data architecture
VAT-exempt under section 19 of the German VAT Act
Build an API
Your application receives a documented API for controlled reading and modification of one defined data area.
US$2,799.00
Total price · one-offVAT-exempt under section 19 of the German VAT Act
- Develop up to five REST endpoints for one data area
- Connect validated request and response formats with existing authentication
- Implement permission checks, error responses and bounded result lists
Your enquiry is non-binding. An order is created only when you accept our quotation .
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Service scope
Your result
- A limited documented API in the existing backend
- Testable data contracts and tests for permitted and rejected requests
Included
- Develop up to five REST endpoints for one data area
- Connect validated request and response formats with existing authentication
- Implement permission checks, error responses and bounded result lists
- API documentation, integration tests and one correction round
Excluded
- A complete backend application or new central user management
- A public developer platform with billing and key management
- Unlimited existing-data migration or high-load guarantees
Which projects does this service suit?
Suitable if …
- An existing data area should become accessible to a frontend or partners
- An application needs clearly defined read and write access
Not suitable if …
- The data model and business processes are entirely unresolved
- A publicly scalable API platform should be created as a complete product
Possible overlaps with: Build a client portal. If you enquire about these services for the same project, we check for duplicated work before commissioning. Your selection also shows a notice.
What this covers
How do we make our data available to other applications under control?
A custom API defines which data may be read and which actions triggered. It may connect an existing backend to a new web interface. The package develops up to five endpoints for one clearly defined data area within your existing application.
Formats, permissions and errors are explicitly described. A frontend must not decide alone which records a user can see. The API checks agreed access server-side and rejects unauthorised requests clearly. New central authentication is excluded.
A data contract makes the API usable
API users need reliable field, filter and response information. We define this contract before implementation, including empty results, invalid input and missing permission. Result lists are appropriately limited rather than returning unlimited data at once.
Endpoints use the existing data model. If structure or business logic still needs creating, that work is scoped separately. Documentation and tests then help coordinate API changes deliberately with consumers.
Does this sound familiar?
A new interface needs existing data
Frontend and backend should cooperate through a defined contract. We limit actions and fields to those actually needed.
Partners should use a data area
Not all internal data may be published. Permissions, allowed fields and access method are defined before technical implementation.
Existing access is inconsistent
Different response formats complicate integration. Shared data and error structures are documented for the agreed area.
How we approach it.
Define actions and the data contract
We define endpoints around specific use cases. Fields, filters, roles and expected error responses form implementation's basis.
Develop backend endpoints
Validation and access checks connect to the existing system. Lists and write actions have clear rules and limits.
Test and document the contract
Integration tests check normal requests, invalid values and missing permissions. Documentation includes intended usage examples.
After handover
The API extends an existing backend area. It replaces neither complete architecture review nor general security approval of the application.
Format changes may affect connected applications. Versioning and later contract changes are described for the agreed use.
Describe the intended function and an example of a successful process. Name existing systems and the roles involved without sharing real customer data or credentials.
After your enquiry, we clarify which data the function processes, which rules it must follow and which systems it must contact. Required documents and test access are agreed separately.
Terms used in this service
What does that mean?
- REST endpoint
- HTTP access to a resource or action. Its contract describes method, format and possible responses.
- Server validation
- Authoritative checking of incoming backend data. It must not assume that a browser supplied valid values already.
- Pagination
- Splitting longer result lists into bounded sections. This makes retrieval manageable and prevents uncontrolled response sizes.
Before your enquiry
Questions about the offer.
What is included, what do you need and what happens after your enquiry?
The process in detail →Is a database included?
The package requires an existing data area. A new model or major schema changes are planned separately, not silently absorbed into API work.
Can external users sign in?
Existing authentication is used. New registration, account recovery and role management belong to the accounts and permissions service.
Will our frontend receive documentation?
Yes. Endpoints, formats and relevant responses are described with examples so integration need not rely on assumptions about the server.
Is a specific load capacity promised?
No general capacity assurance is made without a defined load profile. Agreed access is tested; specialised load tests and scaling need their own scope.
Can the API be extended later?
Yes, within the chosen architecture. New areas and actions still need fresh definition of permissions, data contract and tests.
When does work begin?
We confirm the start and delivery deadline in writing after reviewing your documents. The agreed scope and complete source data determine the schedule.
Which access is needed?
An existing backend with data model and defined access concept Specific actions, user roles and examples of required data Credentials must not be included in the enquiry. Details are agreed only after written commissioning.
What happens after handover?
One written follow-up round is included. The service scope lists the analyses, designs or technical changes covered by the package. We agree additional work with you before it begins.
Read more on this topic
Connecting an API: what to settle before integration
Can the existing API create the order you need? Clarify data fields, access rights and handling of missing responses before integration.
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