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Custom API integrations

Custom API Integrations and Data Synchronization

Connect applications directly when there is no connector, when the connector is too limited, or when the data is too important to trust to a fragile workaround — with authentication, validation, logging and retries designed in.

REST APIsWebhooksOAuth 2.0Data mappingValidationLogging & retries

Overview

Reliable connections between the systems you depend on

An integration is more than an API call. It needs secure authentication, a clear mapping between each system’s fields, validation before data is written, handling for rate limits and temporary outages, and a record of what happened so problems can be diagnosed.

We build integrations using the method that fits: an automation platform with custom HTTP steps, Google Apps Script, or small custom services. The emphasis is on predictable behavior — the same input always produces the same result, and failures are reported rather than silently dropped.

Signs you need this service

  • Two systems hold different versions of the same customer or order.
  • The app you need has no Zapier, Make or n8n connector.
  • An existing integration occasionally creates duplicates or loses records.
  • You export CSV files from one system to import into another.
  • You need to receive webhooks from a payment, booking or e-commerce platform.

Problems we solve

Integration problems we solve

Data out of sync

Customers, orders or payments that differ between systems because updates only flow one way — or not at all.

Duplicate records

Retries and repeated webhook deliveries that create the same record twice.

Silent failures

Integrations that fail on one bad record and stop, with no alert or log.

Insecure setups

API keys pasted into spreadsheets or shared by email, and webhooks that accept any request.

Rate limits and timeouts

Bulk syncs that hit API limits and quit halfway through.

Mismatched data models

Fields, IDs, statuses and formats that do not map one-to-one between systems.

What we build

What an integration includes

Authentication

OAuth 2.0 flows, API keys and tokens stored securely and refreshed automatically where supported.

Webhooks

Endpoints that verify signatures where offered, respond quickly and process events safely.

Data mapping

A documented field map with transformations for formats, units, statuses and IDs.

Validation

Required fields, types and business rules checked before anything is written.

Idempotency & retries

Protection against duplicates, exponential backoff for rate limits and temporary errors.

Logging & alerts

A record of each sync, clear error messages and alerts when attention is needed.

Sample workflow

Sample workflow: payments to accounting and reporting

This example shows the structure of a payment integration — the kind of flow used to move point-of-sale or online payments into accounting records and a management report.

An idempotency check on the payment ID ensures that a repeated webhook delivery never creates a second entry.

This is a hypothetical example built to explain the approach. It is not a description of a specific client project.

Demonstration — sample data, not a client project

Payment webhook → validate → accounting → report

  1. 1Webhook receivedPayment platform sends a “payment completed” eventwaiting
  2. 2Signature verifiedRequest authenticity checked before processingwaiting
  3. 3Duplicate checkPayment ID looked up in the sync logwaiting
  4. 4Data mappedAmounts, fees, tax and customer mapped to accounting fieldswaiting
  5. 5Records writtenSales receipt created; report sheet updatedwaiting
  6. 6Result loggedSuccess or failure recorded with a referencewaiting
Press “Run the workflow” to watch the sample data move through each step.

How this workflow is specified

Trigger
Webhook event from the payment platform, with a scheduled reconciliation job as a safety net.
Applications
Payment or POS platform, accounting software, Google Sheets or database, alert channel.
Data inputs
Payment ID, amount, currency, fees, taxes, customer, location, timestamp.
Processing logic
Verify signature, check for duplicates, map fields, create accounting record, update report, log result.
Expected outputs
One accounting entry per payment, an updated report and a log entry.
Failure points
Invalid signatures, duplicate deliveries, accounting API validation errors, expired OAuth tokens, rate limits.
Error handling
Idempotency key, retries with backoff, failed events stored for replay, alert after repeated failures.
Testing
Sandbox accounts where available, replayed sample events, forced errors and a reconciliation comparison.

Platforms & tools

Systems we commonly connect

If an application has a documented API or can send webhooks, it can usually be integrated. We confirm API access, plan limits and authentication requirements during discovery.

REST & JSONWebhooksOAuth 2.0GoHighLevel APIGoogle Workspace APIsSquare APIStripeTwilioRingCentralTookanQuickBooks / XeroShopify / WooCommerce

Implementation process

How an integration project runs

  1. Discovery call

    We review the current process, the applications involved and the outcome you need, and ask for examples of real (or anonymized) records.

  2. Written scope

    You receive a short plan: trigger, steps, data fields, error handling, what is included and what is out of scope.

  3. Build

    We build against sandbox or test accounts where available, with credentials stored in a secure configuration rather than in code or spreadsheets.

  4. Test

    Normal, edge and failure cases are tested — missing fields, duplicates, bad formats and authentication problems.

  5. Go live

    The workflow is switched on with you, checked against live activity and monitored during the first days.

  6. Handover

    You receive notes on how it works, where logs live, how to pause it and what to check if something changes.

Practical considerations

Practical considerations

  • Every API has its own limits, permissions and plan requirements; some features require a higher subscription tier in the source application.
  • APIs change over time; integrations need occasional maintenance when providers release new versions or deprecate old ones.
  • Two-way sync requires clear rules about which system wins when records conflict.
  • Where available, we build and test in sandbox environments before touching live data.

Troubleshooting

When data stops syncing

Integration failures leave evidence. We look at:

  • HTTP status codes — 401/403 (authentication), 404 (wrong resource), 422 (validation), 429 (rate limit), 5xx (provider issue).
  • Request and response bodies — what was sent and what the API said about it.
  • Webhook delivery logs — whether the provider sent the event and what response it received.
  • Token status — expired or revoked OAuth tokens.
  • Recent changes — new required fields, API versions or renamed values.

Integration troubleshooting

FAQ

API integration questions

Do you need our passwords?

No. We use API keys, OAuth authorization or user invitations with appropriate permissions, shared through a secure method — never plain chat or email.

Where does the integration run?

Depending on the design: inside an automation platform you own, in Google Apps Script, or on a small server or cloud function. We explain hosting and costs before building.

Can you integrate with our custom or internal software?

If it exposes an API, a database connection or can send webhooks, usually yes. If not, we discuss alternatives such as scheduled file exchange.

How do you prevent duplicate records?

By matching on stable identifiers, storing processed event IDs and using “find or create” logic, so repeated events do not create repeated records.

What happens when an API changes?

Logging and alerts make the failure visible quickly. Maintenance can be arranged to update the integration when providers change their APIs.

Guides

Related troubleshooting guides and tutorials

CRM Data Not Syncing Between Applications? Common Causes

Why records go missing, duplicate, or go stale between your CRM and other apps, how to trace the cause, and how to reconcile data after the fix.

Read the guide

Need two systems to finally agree?

Tell us which applications are involved, what data should move and how often.

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