How to scope a .NET API integration before estimating it

A useful first integration scope names one business event, one direction of data flow, the required fields, and how a safe test will prove the result. This hypothetical example uses synthetic data; it is a planning aid, not a Flextech customer project or a promise that any two systems can be connected.

Hypothetical example — synthetic data only. “Sample Parts Co.” has an existing .NET order application. Its owner wants an approved invoice sent to a separate accounting service. No real company, software vendor, database, or customer record is represented here.

Start with one event and one direction

Instead of asking for “an accounting integration,” define the first event precisely: when an invoice in the source application reaches an agreed approved state, send that invoice once to the destination system. The example is one-way. It does not assume that the destination has an API, that the source exposes one, or that either system permits this flow. Even if the .NET application stores records in SQL Server, do not assume that a direct database write is supported or safer than the application interface. Any read-only SQL inspection needs owner approval and schema context; database writes or schema changes require separate assessment.

Write down the field mapping

A small field map exposes missing decisions before code is changed. These values are invented examples, not a recommended accounting format.

Do not send live customer information just to explain the mapping. A sanitized schema or synthetic row is enough for an initial discussion.

Define behavior when things go wrong

Integrations need decisions for repeated events and failed requests, not just the successful path. For this example, agree how a repeated invoice event is recognized, what happens after a timeout, which errors a staff member can see, and who is allowed to retry. The actual approach depends on the source and destination capabilities.

• Duplicate handling: identify a stable invoice key and test the agreed behavior when the same event is received twice.
• Failure visibility: make an unsuccessful transfer visible with a reference that helps an authorized person investigate. Do not log passwords, API keys, tokens, or unnecessary personal data.
• Retry and correction: decide whether a user can retry, who resolves invalid fields, and how a corrected invoice is distinguished from a new one.
• Human approval: confirm who approves the test result and who authorizes any later production write.

Example acceptance checks for a first test

Acceptance should be observable and agreed before implementation. A safe test plan for the synthetic example could check:

1. Only the agreed approved test invoice is sent from the test source to the test destination.
2. The destination shows the expected reference, date, currency, amount and customer mapping.
3. Repeating the same event follows the agreed duplicate rule and does not silently create an unintended second invoice.
4. A deliberately invalid test value or unavailable test endpoint produces a visible, traceable failure and follows the agreed retry rule.
5. The owner reviews the result and separately approves any production access or write before it is enabled.

Passing these checks would confirm only the agreed test cases. It would not certify either system's security, accounting treatment, tax compliance, or every future scenario.

What must be ready before a real estimate

• A named owner for the .NET source system and permission to review the relevant code or supported interface.
• The .NET/runtime version, current behavior, one target outcome and any known error example, sanitized.
• Official API documentation, authentication method and the minimum read/write permissions available.
• Field definitions and a synthetic or anonymized sample; no customer exports or secrets.
• A sandbox or other safe test route, plus the person who can approve test access and acceptance.
• Deployment owner, rollback approach and an explicit decision on whether production changes are in scope.

If documentation, ownership, permission or a safe test path is missing, pause at discovery. Do not guess how a private API works or promise compatibility before it has been assessed.

Keep the first scope bounded

A first written scope might cover one source, one destination, one invoice event, an agreed field map, safe test cases, visible failure handling and a documented handoff—only if both systems support that approach. Two-way synchronization, historical backfill, multiple record types, redesigning either application, schema migrations, security certification, accounting advice and ongoing support should be assessed and quoted separately if needed.

For the wider custom-software process, see custom software development in Malaysia. For the factors that affect an estimate, see the custom software cost guide.