API architecture and system integration | Anexia

For system integration, business objects, identities and responsibilities are clarified first. A technically valid message can be useless from a business perspective if, for example, status values or time zones are interpreted differently. The contract therefore describes meaning, permitted values and behaviour in the case of incomplete information. Authentication and authorisation are designed to suit the systems involved.

In API engineering, we consider timeouts, retries and partially successful operations. A calling system must know whether an action may be sent again or may already have been executed. For API integration, suitable keys, responses and reconciliation procedures are provided. Changes to the contract require a traceable versioning and transition strategy. The tests cover permitted and impermissible states as well as realistic error responses. In this way, the interface architecture becomes a resilient link between business processes whose behaviour remains understandable even when one of the systems involved temporarily does not respond correctly.

Scope of services for API integration

The agreed scope for system integration can include the following deliverables: API contracts, data mapping, authentication, error concept, versioning rules and integration tests. For each key deliverable, we define what it is for, who reviews it and in what form it is handed over. This allows development, operations and procurement to assess the same service. Vague umbrella terms in the offer are replaced by concrete work packages.

API engineering also includes coordinating the necessary interfaces with your team. We clarify access, contacts and available testing options before the relevant implementation steps. Changes to the scope are described together with their impact on effort and sequence. This gives you a traceable overview of delivered results, prerequisites still outstanding and additional requests.

The key technical decision in API integration

Synchronous calls and event-based processing are weighed up for each business process. Decoupling in time changes the requirements for consistency and user information. For the interface architecture, we document the relevant assumptions and explain the reasons for the chosen variant. Key alternatives are considered against the same business requirements. This makes later adjustments easier when load, data volume or organisational responsibility change.

A sound decision also takes maintainability and handover into account. For system integration, we check which skills are available internally and what additional support is needed. This links technical possibilities with a realistic operating model. The client can see which tasks will arise regularly after the project and which decisions remain with them.

A timeout can occur even though the target system has already carried out the change. Uncontrolled retries then create duplicate transactions. In API engineering, we treat this point as a concrete test question. A risk is linked to the affected process, its possible impact and a suitable measure. Where prerequisites are still missing, the statement is explicitly left open until the necessary investigation has taken place.

We check duplicates, delayed messages, changes in order, schema changes and the business tracking of a transaction. For API integration, we record the initial situation, the tested configuration and the result. Acceptance relates to the agreed scope. Open limitations are documented visibly and assigned to a next step with a clear owner. This allows your team to distinguish between proven functionality, a deliberate decision and an assumption not yet confirmed.

Project example as an illustrative scenario

The following scenario is an example application, not a customer reference. A company connects its online shop, merchandise management and logistics, but receives contradictory status messages for orders. With API integration, a complete order would be tracked across all systems involved. Individual calls that succeed technically could still result in a transaction that is incomplete from a business perspective. The pilot would therefore have to make states and responsibility visible for each transfer.

For the interface architecture, unique transaction identifiers and rules for retries, order and outdated messages would be agreed. One test case could represent a timeout after a booking has already been made. A repeated call must not create the same order again. Further checks would cover delayed delivery notifications, unknown items and a recipient that is temporarily unreachable. Errors would have to be stored in such a way that they can be reprocessed in a targeted way once clarified. Interface changes would take the consumers already connected into account.

Acceptance of the system integration would check transactions completed from a business perspective and understandable exception states. Planned results would be versioned contracts, traceable data sovereignty and a controlled reprocessing path. In the event of a fault, the team would have to be able to see at which transfer a transaction is stuck and which action is permitted. A mere success rate of technical HTTP calls would not be enough for this. What would matter is whether order, stock and delivery are handled consistently across system boundaries.

Our experience and our engineering approach

We combine custom software development with the technical tasks of introduction and further development. For the interface architecture, we bring the perspectives of application, integration and operations together in a shared workflow. The business requirements remain connected to the technical decisions. You work with a defined scope of services and traceable results.

Our experience should become concretely verifiable for your project. That is why, in the technical exchange, we explain how we investigate the relevant risks, which deliverables are planned and how your team can assess them. For system integration, we align the roles involved with actual needs. Available references are presented with their specific project and company context; confidential customer details are not used as general advertising claims.

Effort for system integration

The number of systems, data models, frequency of change and quality of existing interfaces determine the scope. We therefore calculate API integration based on a delimited scope and explicitly stated prerequisites. An initial analysis step can make sense if key technical information is still missing. After that, work packages and acceptance criteria can be agreed on a more reliable basis.

The interface architecture work can be organised as a limited project, as a joint implementation with your team or with subsequent support. Rights of use, access, documentation and responsibilities are clarified in the contract. Ongoing operating hours, response times and external consumption costs are covered by separate agreements. This keeps it clear which services are provided once and which tasks arise regularly after introduction.

Boundaries of API integration

The mere technical availability of an API does not replace business alignment of its data and states. For API engineering, we set out this boundary in the offer itself. Any additional services required are included with their business justification and are not silently assumed. This allows your team to plan suitable internal skills and divide the overall work sensibly between those involved.