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APIs & Integrations

Most integration problems are really data-consistency problems: two systems holding different versions of the same record, reconciled by someone re-typing it. Appex Technology designs and builds custom REST and GraphQL APIs, webhook pipelines, and third-party integrations that keep systems in agreement automatically — including with legacy tools that never shipped a modern API.

Start a projectHow we work
Custom API design & development
Third-party & payment integrations
Data sync, ETL & webhooks
What you get

What we actually deliver

  • Custom APIsVersioned, documented REST or GraphQL interfaces designed for the consumers that will actually use them.
  • Third-party integrationsConnections to payment, CRM, accounting, messaging, and logistics services, with real error handling.
  • Webhooks and event pipelinesEvent-driven syncing with retries and idempotency, so a failed delivery does not silently corrupt state.
  • Data sync and ETLScheduled or streaming pipelines between applications, warehouses, and databases.
  • Legacy bridgesAdapters for systems predating modern APIs, via database access or structured file exchange.
Who it’s for

A good fit if…

  • Teams re-entering the same information into two or more systems
  • Businesses whose tools each hold a partial, slightly different version of the truth
  • Companies needing to expose an API to their own customers or partners
  • Operations depending on a legacy or internal system with no modern interface
How it works

From first call to handover

  1. Step 01

    Map the data

    Which system owns each record, and what should happen when two disagree — decided explicitly rather than discovered in production.

  2. Step 02

    Design the contract

    Endpoints, payloads, auth, and versioning agreed before implementation.

  3. Step 03

    Build for failure

    Retries, idempotency, and alerting, because third-party APIs go down and yours should degrade rather than break.

  4. Step 04

    Document and monitor

    Reference docs for consumers and monitoring that surfaces a broken sync before a customer reports it.

Often built with

Platforms we pair with this

n8n

Self-hosted workflow automation that connects your tools and removes manual, repetitive work.

Replaces Zapier

Activepieces

An open automation builder for internal ops and AI-driven workflows, hosted on your cloud.

Replaces Make, Zapier

Windmill

Turn scripts into internal tools, workflows, and UIs — a developer-first automation platform.

Replaces Retool, internal tools

Novu

A notification layer for email, SMS, push, and in-app — unified and self-hosted.

Replaces Courier, OneSignal

Supabase

Postgres database, auth, storage, and realtime APIs — the backbone of many of our builds.

Replaces Firebase

FAQ

APIs & Integrations — common questions

Can you integrate with a system that has no API?+
Usually. Options include direct database access where that is safe, structured file exchange on a schedule, or an adapter service that wraps the legacy system in a modern interface. Screen-scraping is a last resort and we will flag its fragility clearly before relying on it.
REST or GraphQL?+
REST suits most cases and is simpler to cache, document, and debug. GraphQL earns its extra complexity when many different clients need different shapes of the same data, or when over-fetching across a deep object graph is a real performance problem. We pick per project rather than by default.
What happens when a third-party API goes down?+
Integrations are built assuming it will. Failed calls are retried with backoff, operations are made idempotent so retries cannot double-charge or duplicate records, and failures alert someone rather than disappearing. Degrading gracefully matters more than any individual uptime number.
Can you build an API for our customers to use?+
Yes — public and partner APIs are common work, and they carry requirements internal ones do not: versioning so you can change things without breaking consumers, authentication and rate limiting, and documentation good enough that someone can integrate without contacting you.
How do you handle data that exists in two systems?+
By deciding which system owns each field before writing any code. Most sync problems are really unresolved ownership questions, and they surface as records that silently drift apart. We settle that in scoping, then enforce it in the pipeline.
Related reading

More on this topic

Why API-First Architecture Saves Money Long Term

What API-first architecture means, why it lowers long-term cost and risk, and how building behind your own API layer keeps your software flexible and lock-in free.

Integrating Stripe Into a Custom App: A Practical Guide

How to add Stripe payments to a custom application the right way — one-time payments vs subscriptions, webhooks, and the pitfalls that break billing.

Migrating Off a SaaS Tool: A Safe Data Migration Playbook

A step-by-step playbook for migrating data off a SaaS tool safely — exporting, mapping, validating, and cutting over without losing records or downtime.

Modernizing Legacy Software Without a Risky Rewrite

How to modernize legacy systems without a dangerous big-bang rewrite — the strangler-fig approach, where to start, and how to reduce risk while keeping the business running.

Other services

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Need apis & integrations?

Tell us what you're trying to build — we'll scope it and send a fixed estimate before any work starts.

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