API Integration Services: Connect the Systems You Already Run
Your accounting, CRM, ERP, e-commerce and messaging tools each hold part of the truth, and someone on your team copies data between them. We build the integrations that do it for them, starting with one flow, with every write traceable and every failure reported to a person.
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Integrations we run in production
Not a list of logos: these are connections we built, run, and fix when the other side changes.
QuickBooks Online and Desktop
Orders turned into draft invoices that are created only after a person approves the total. Desktop through the Web Connector and qbXML. The code is open source.
How it works →WhatsApp and Telegram
Messages and voice notes received through Meta's Cloud API and the Telegram Bot API, transcribed, routed to the right workflow, and answered.
The voice-to-order case study →E-signature
A service in front of SignWell that registers callback URLs, forwards signature requests and relays each webhook back to the application that asked, optionally RSA-signed.
Microsoft sign-in and Slack
A shipping platform where the team signs in with its Microsoft accounts and gets a Slack message on every new request, in production the day after we received the workbook it replaced.
The shipping platform case study →Payments and marketplaces
Payment provider callbacks and marketplace order APIs feeding the fulfilment of an online store, with every order traceable from the payment to the delivery.
AI assistants, through MCP
Our own CRM exposes more than 160 tools to Claude, each running with the signed-in user's permissions. We build the same for other systems.
MCP server examples →
Signs you need an integration
- Someone retypes the same order, invoice or customer into a second system every day.
- A nightly CSV export and import holds the business together, and nobody notices when it fails.
- Your Zapier or Make account has grown into dozens of zaps nobody fully understands, and the bill grows with it.
- The vendor you depend on has no connector for the other tool you use, or the connector skips the fields you need.
- Numbers disagree between systems and the month-end close starts with finding out which one is right.
And when not to build one: if a native connector or an app from the vendor's marketplace already moves the data you need, use it. We will tell you so on the first call.
Four ways to connect two systems
Most integration problems don't need custom code. The right option depends on how much logic sits between the two systems.
| Option | What it means | When it fits |
|---|---|---|
| Native connector | An integration built by one of the two vendors, or an app from their marketplace. | Common pairs (Shopify and QuickBooks, HubSpot and Gmail) where the standard fields are enough. |
| Integration platform | Zapier, Make or n8n: triggers and actions wired together without code, or with a little. | Simple flows with low volume, where a missed run is an inconvenience rather than a loss. |
| Custom integration | Code that reads from one system, applies your rules and writes to the other, with retries, logs and alerts. | Business rules, matching between records, legacy or custom systems, volumes where reliability matters. |
| MCP server | Your system exposed as typed, permissioned tools that AI assistants such as Claude or ChatGPT can call. | When people should be able to ask an assistant to read or update the system, with a person approving the writes. |
We start every project by checking whether option one or two would do. An integration platform is often the right answer, and our comparison of Zapier and n8n is a good place to start. n8n vs Zapier →
How we build an integration
One flow first, live and measured, then the next one.
- 1
Map the flow and the source of truth
Which system owns each field, what triggers a sync, what has to happen when a record exists on one side only, and who needs to know when something fails.
- 2
Build on your real data
We run the first version against copies of your real records, not samples. Matching rules are tested on the messy cases: duplicates, renamed customers, items spelled three ways.
- 3
Go live with a person in the loop
Writes that matter wait for approval at first. Every sync is logged with the IDs on both sides, and failures alert a named person rather than disappearing.
- 4
Run it
APIs change, tokens expire, vendors deprecate versions. We monitor the integration, apply updates and fix what breaks, or hand it over to your team with the documentation.
What makes an integration last
- Every field has one owner. Two systems allowed to edit the same field is how numbers start to disagree.
- Writes are idempotent: a retry never creates a second invoice, order or contact.
- Only errors that can succeed are retried. A billing or permission error fails at once and tells someone, instead of being retried in a loop.
- Every record keeps the other system's ID, so any line can be traced from one side to the other in one lookup.
- Anything ambiguous is flagged for a person, never guessed: a name that matches two customers, an item that doesn't exist on the other side.
How much do API integration services cost?
These are the ranges we work to, in US dollars. A custom integration has no per-task fee like an integration platform, but it does have running costs, and we list them too.
| Scope | Budget | What you get |
|---|---|---|
| First flow, live | $5,000 to 18,000 | One integration in production, such as orders from your store into QuickBooks or deals from your CRM into your ERP, with logs and alerts. |
| Several flows | $18,000 to 45,000 | Two-way sync across several systems, data migration, approval steps and a reconciliation report. |
| Hosting | $50 to 100 / month | The integration running on our platform or in a cloud account you own. |
| Maintenance | from $470 / month | Monitoring, API and token updates, fixes, and small changes as your process evolves. |
A half-day scoping workshop (about $2,300 to $4,700, credited against the first flow) fixes the scope and the price before anything is built.
Frequently asked questions
What are API integration services?
API integration services connect software systems through their APIs so data moves between them without anyone retyping it: orders from a store into accounting, deals from a CRM into an ERP, messages from WhatsApp into a CRM. The work covers mapping which system owns which data, building the connection, handling errors, and keeping it running when the APIs change.
How much does an API integration cost?
At Reflekt Lab, a first integration flow in production costs $5,000 to $18,000, and several flows with two-way sync $18,000 to $45,000, then about $50 to $100 a month for hosting and from about $470 a month for maintenance. A native connector or an integration platform is cheaper when it covers your case.
Should we use Zapier or a custom integration?
Use Zapier, Make or n8n for simple, low-volume flows where a missed run is an inconvenience. Choose a custom integration when business rules sit between the systems, records have to be matched, volume is high, a failure costs money, or one side is a legacy or custom system without a connector.
Can you integrate a system that has no API?
Often, yes. Older systems can usually be reached through a database, file exports, a desktop connector such as the QuickBooks Web Connector, or an email inbox. We assess which route is reliable before quoting.
How long does an integration take?
A first flow is usually live in two to four weeks after scoping. A program of several flows is delivered in stages over a few months, each one used before the next starts.
What happens when one of the APIs changes?
Integrations break when vendors change versions, retire endpoints or expire tokens. With maintenance, we monitor for that and update the integration; without it, the code and documentation are yours and any developer can take it over.
Tell us which two systems should talk
Name the systems, what moves between them today and who copies it. On a 30-minute call we'll tell you whether a connector covers it and what a custom integration would take.
