An API is the door through which one piece of software lets another read or write data. Without that door, two systems cannot talk — no matter how much money you spend.
Which is why “does it have an API?” belongs before you buy software, not at the point where you need to connect it to something.
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What it is, without the jargon
Picture a restaurant. The customer does not walk into the kitchen — they speak to a waiter, who knows what can be asked for and how.
An API is the waiter: a controlled way to ask a system for specific things, without touching its internals.
In practice, an API lets things like this happen:
- A new order in the e-shop automatically creates an invoice in your accounting system.
- Stock levels in the ERP update availability on the site every fifteen minutes.
- A form enquiry becomes a record in the CRM with the right person assigned.
The three kinds of connection
You do not always need development. There are three levels, at very different costs.
| Kind | What it is | Cost | When it fits |
|---|---|---|---|
| Ready-made integration | The vendor offers it in one click | €0 – €200 | Popular combinations |
| Automation tool | Middleware joining the two | €10 – €50/month | Low volume, simple flow |
| Custom connection | Written specifically for you | €500 – €5,000 | Specialist systems, volume |
Always check in that order. Plenty of businesses pay for development of something that already existed in an integrations list nobody opened.
The second level covers more cases than you would expect — see what works and where it stops in Zapier & Make.
How to tell whether a system has a usable API
“We have an API” means nothing on its own. Ask for these five, in writing:
- Public documentation. With no instructions page, development happens by trial and error — and you pay for it.
- A test environment. So the connection can be tried without damaging real data.
- What it allows. Read only, or write as well? Which fields?
- Rate limits. How many requests per minute or day. This decides whether it handles your volume.
- Change notifications. Does the system push an update when something happens, or must you keep asking?
The fifth makes a large difference to the experience: a connection that gets notified is nearly instant; one that polls every fifteen minutes is always slightly behind.
What a connection costs
| Component | Indicative range |
|---|---|
| Analysis and design | €200 – €800 |
| Building a simple connection | €500 – €1,500 |
| Building a complex connection | €1,500 – €5,000 |
| Testing and fixes | 15%–25% of the project |
| Annual maintenance | 10%–20% of the build cost |
The last row is the one that gets forgotten. APIs change: the vendor releases a new version, retires fields, changes how authentication works. A connection with no maintenance budget breaks eventually, usually at peak.
The same five-year cost logic applies to the wider decision — see custom software vs off-the-shelf.
Want an estimate for a specific connection?
Tell us which two systems you want joined and we will tell you what it takes.
The six questions to ask before buying software
Put these in every evaluation, even if you have no plans to connect anything today:
- “Is there an API and where is its documentation?”
- “Is it charged separately?” With several vendors it sits in a higher tier.
- “Which ready-made integrations already exist?”
- “How do I export all my data if I leave?”
- “How often does the API change and how are we notified?”
- “Who supports the connection when it breaks?”
The second surprises people: plenty of systems grant API access only on their most expensive plans. Discover that after purchase and your options are an upgrade or manual work forever.
What usually goes wrong
Five causes covering nearly every failure:
- Data mismatch. One system says “Ioannina”, the other “IOANNINA”, and records duplicate.
- No error handling. When a call fails, nobody finds out and orders go missing.
- Unclear direction. Which system is the source of truth for price? Undefined, and they will overwrite each other.
- Hitting rate limits at peak hour, so the connection stops exactly when you need it.
- No logging. Without a history, “why didn’t this order come through” never gets answered.
The third is the most serious and it is not technical — it is a decision. Before any connection, define which system “wins” for each field. In practice that reveals how your business actually runs: see the example in ERP to e-shop integration and in inventory management.
Frequently asked questions
Do I need a developer for every connection?
No. Popular tools have ready-made integrations or no-code options. A developer is needed for specialist systems and high volume.
How long does a connection take?
Simple: 1–2 weeks. Complex, involving an ERP: 4–10 weeks, with most of the time in testing.
Is it secure?
With proper access keys, limited permissions and encryption, yes. The risk is not the API — it is keys circulating in email.
What happens if I change provider?
The connection gets rewritten. Which is why the data export question matters before you buy.
Do Greek systems have APIs?
Most modern ones do — with varying documentation quality. Ask to see it in writing before committing.
The first step
List the systems you use and note beside each one: information that gets typed in twice.
Every such double entry is a candidate connection — and how many there are tells you whether you need an automation tool or a proper integration.
Next step
Book a free 30-minute call with the team at The Dev Alley. We will look at your systems and tell you what connects easily and what does not.