Payment gateway integration blends security engineering, payment rail knowledge, and SEPA rules. It takes an agency that's done this before, so that your project doesn’t become a training ground and reduce your time-to-market.
Let’s take a look at what makes payment integration hard today, what's always made it hard, and what a strong agency looks like.
TL;DR
AI speeds up integration, but security concerns hold back full trust,
Europe's Instant Payments Regulation isn't optional,
Security, scalability, and vendor lock-in are permanent risks,
The right agency can prove its claims with past projects.
AI is helping with integrations, but not trust
A Payroc survey of 750 software leaders and developers in the US, UK, and Canada found 97% have lost revenue to slow or complex integrations.
At the same time, 96% of them say AI has sped up integration.
Yet, 43% of them name security as the top barrier to AI-powered integration.
The EU adds a legal deadline.
SEPA Instant has been mandatory for euro-area providers since January 2025 under the EU's Instant Payments Regulation, with further deadlines running through 2027.
Risks that outlast any regulatory deadline
Security, scalability, and vendor lock-in predate AI and the Instant Payments Regulation.
Security means more than encryption.
Marilyn McDonald is the CTO at Thredd, which processes payments for over 100 fintechs and digital banks.
"The accountability for any change has to sit with a person rather than a machine." - Marilyn McDonald, CTO at Thredd
Alongside that rule, Thredd keeps an audit trail a regulator can trace.
Scalability is less about traffic than geography.
An integration built around one market's currencies and rails can turn expansion into a rebuild.
The original build decides whether that happens.
In addition to that, you often end up choosing your future partners when you choose your technolog.
In 2017, Verto co-founder and CTO/CPO Anthony Oduu planned a blockchain platform for B2B payments.
The banking partners Verto needed would not work with blockchain for regulatory reasons, so he dropped the plan.
Vendor lock-in starts in architecture decisions.
What a strong integration agency brings
The Software House's Adyen integration for the subscription management platform Cleeng is one example.
Custom work when standard SDKs fall short
Adyen's standard SDKs work for many companies.
Cleeng had more specific data handling needs.
The integration became a custom layer built to meet security, scalability, performance, and time-to-market requirements.
A good agency can tell you when a standard integration will work and when it won't.
Security in Cleeng's integration
The build used throttling to cap requests per user and rate limiting to cap load on the whole service.
It added least-privilege access and AWS Secrets Manager for credentials.
None of these techniques is new on its own.
The hard part is applying all of them under a strict deadline.
A track record that outlasts one project
The integration shipped on time and was built for traffic spikes and future extensions.
The Software House has worked with Cleeng for 4 years.
An agency that clients invite back after a first project belongs on your shortlist.
Narrowing down your shortlist
Choosing a payment gateway partner for a European fintech means weighing AI speed against security concerns.
The same choice means planning for the Instant Payments Regulation deadlines as well as for security, scalability, and vendor lock-in risks.
The agency worth hiring can show evidence on each of these points, not just one of them.
It has a lot of experience, evident in the projects it has completed and the tools it uses, allowing you to put your initial trust in it.
It starts with strong architecting to design a solution that can be easily extended or changed (i.e., by making it easy to swap third-party vendors).
However, it does it all in a way that doesn’t slow you down in the first weeks or months.
The Software House's fintech team has built payment integrations on SEPA, Adyen, and AWS projects.
If you're weighing a project of your own, get in touch to talk through what it needs.
Authors
Adrian Senecki
Copywriter and budding fiction writer, interested in (but not limited to) the business side of software development. Likes acquiring new skills and foretelling the future.
Andrzej Wysoczański
Frontend developer with 10 years of experience. With The Software House for almost 7 years, going from a regular dev to the Head of Frontend. He loves keeping tabs on the latest frontend technologies, especially React-related. Regular of the Taby & Spacje podcast (tsh.io/taby-vs-spacje) for Polish speaking programmers.