APIs and system connections
Are you still retyping website data into another system?
I connect websites and e-shops with invoicing, payment gateways, email platforms and internal systems, so data moves automatically with logging and error handling.
Manual retyping is the most expensive integration a company can run. An order arrives by email, someone copies it into the invoicing system, pastes the address into the courier tool, adds the contact to the newsletter and notes the status in a spreadsheet. Every step costs time and every step invites a typo that surfaces later in a complaint or in the accounts. Connecting systems over an API removes that chain. Data is created once, in one place, and moves onwards automatically in an agreed shape. I build integrations as daily work, so I know most of the effort is not in the happy path. It is in what happens when the remote service is unavailable, returns an error or quietly changes the format of its response.
I am a freelance developer based in Poprad with 19 years of experience in PHP and web systems. I work remote-first and you speak with me directly. The rate is €40 per hour including VAT. A simpler connection, such as pushing an order into invoicing, usually fits 4 to 10 hours. Two-way synchronisation of stock, prices and statuses with a company system is a larger project, and I only estimate it after reading the documentation of the other side. If that documentation does not exist or the interface is incomplete, I say so before we start and propose a realistic substitute, such as an agreed scheduled export and import.
01
Invoicing and accounting
The most common request is that an order from the website becomes an invoice without anyone retyping it. I connect invoicing services such as SuperFaktura and comparable interfaces, send the document to the customer, store a copy against the order and return the payment status to the shop. I also handle the details that decide whether the result is usable: variable symbols, several VAT rates, credit notes, proforma invoices, numbering series and company details for B2B purchases. For recurring payments I set up documents generated per period. If your accountant needs a batch export, I prepare it in the exact format their software accepts.
- Invoices generated from orders
- VAT rates, credit notes and numbering
- Exports in your accounting format
02
Payment gateways and shipping
I implement a payment gateway so that the payment, its confirmation and any refund match the order status even when the customer closes the browser before returning to the site. That means processing background notifications, verifying the signature of each message and protecting against counting the same payment twice. Shipping works the same way: creating the consignment, printing labels, selecting a pickup point and pulling delivery statuses back. The customer then sees a truthful status and your staff do not have to hunt for it across three different administration panels.
- Payments with background notifications
- Refunds and partial payments
- Labels and delivery statuses
03
Email, CRM and marketing tools
Contacts are worth most when they sit in the right place with the context that matters. I connect the website with tools such as Mailchimp and other email or CRM platforms, carrying over consent records, segmentation based on a purchase or a form, and where useful the order history as well. I set up two-way unsubscribes so that a person who opted out does not reappear in the next campaign through another route. I can also move transactional email to a reliable sending service, which improves deliverability considerably compared with sending straight from shared hosting.
- Contacts, consent and segments
- Two-way unsubscribe handling
- Deliverable transactional email
04
Internal and project systems
Most companies already run something: a stock or ERP system, a project tool, spreadsheets, an attendance system or an in-house database. I connect the website to them so each side keeps the job it does best. Stock and prices can flow from the company system into the website, an enquiry from a form can open a task in the project tool, an approved order can appear in an internal overview. I also work with Google services, most often writing to Sheets, managing calendar entries and reaching documents. When a system has no API, I look for the nearest dependable route: an agreed exchange file, a database view or a scheduled import with content checks.
- Stock, prices and statuses from ERP
- Enquiries into project tools
- Google Sheets, Calendar and Drive
05
Custom REST APIs and dependable operation
When a partner, a mobile app or another website needs data from your system, I build a custom REST API with clear documentation, authentication, versioning and sensible rate limits. I give the same attention to running the integration afterwards: retrying failed transfers, queueing background jobs, keeping a log of calls and alerting you when something stops working. A silent integration you learn about from a customer is worse than none at all. Handover therefore includes a short overview of where transfer status is checked and what to do when the other side is down. The point is that the connection survives the months when nobody is watching it.
- Documented, authenticated REST APIs
- Retries and background job queues
- Transfer logs and failure alerts
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Common questions about API integrations
How much does connecting a website to another system cost?
A simpler one-way integration is usually 4 to 10 hours, while two-way synchronisation with a company system runs from 15 to 40 hours. At €40 per hour including VAT that means roughly €160 upwards. I give a firm estimate after reading the documentation of the other side.
What if the system has no API or documentation?
That happens often. I then look for a substitute route: a scheduled file export and import, direct database access or an interface the vendor can enable on request. If no dependable route exists, I say so plainly rather than promise a connection that would break at every update.
How are outages of the other service handled?
Transfers are designed so an outage does not lose data. A failed call is queued and retried, the error is written to a log and repeated failures trigger an alert. The order waits until the service is reachable again instead of disappearing.
Is this the same as AI integrations?
No. This page covers connecting a website to business systems: invoicing, payments, stock, email and internal tools. AI assistants, text processing and automation built on language models are covered by the separate AI integrations page.
Can you add an integration to a site built by someone else?
Yes, that is a common situation. I first review how the site is built, which versions it runs and whether the change would conflict with updates. I then build the integration so it survives future updates, and hand over a short description of the solution.
Want your systems to hand data to each other?
Tell me which systems you run and what is retyped by hand today. I will say whether they can be connected and at what scope.
Discuss an integration