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You own the path from signed contract to first live transaction.
A merchant signs. Then someone has to read their stack, answer their API questions, debug their callbacks at 3pm on a Tuesday, fix what’s broken on our side, and keep the whole thing moving until money is flowing and the approval rate looks right. That someone is you.
This is a hands-on engineering role, not a coordination role. You will read logs, reproduce issues in sandbox, write the corrected request for the merchant’s developer, and ship fixes in our own services when the root cause is ours. Project management is a means here, not the job.
We are growing the Implementation team in the region, so you will also help define how this works: the tooling, the reusable answers, the escalation paths, and the documentation that stops the same question from being asked twice.
One metric, three dimensions: integrations moved from signed to live transacting.
How many — volume of merchants you take live.
How fast — time from signature to first live transaction.
How well — approval rate on the traffic those integrations bring. An integration that goes live and then underperforms is not a finished integration.
Where You Sit
You report to the Implementation Managers Lead, who reports to the Head of PayCore. Day to day you work alongside Account Managers, who own the commercial relationship, and the engineering teams that own our services, whom you escalate to — and ship with — when the fix is on our side.
Driving integrations to live (≈50%)
Take signed merchants through integration end to end: scope the setup, answer API and configuration questions precisely and in writing, unblock their developers, and stay on it until transactions are flowing.
Investigate problems end to end: read logs, trace requests across services, reproduce in sandbox, and name whether the root cause is our platform, the configuration, or the merchant’s implementation.
Diagnose and explain integration failures: failed callbacks, unexpected response codes, signature and authentication problems, transaction states that don’t match expectations.
Be the technical point of contact for Account Managers, and turn recurring questions into documentation, examples, and internal runbooks.
Fix the merchant’s code with them: review the integration, point at the actual problem, write the corrected request or snippet that makes it work.
Fix bugs in our own services when the root cause is ours, working with the owning engineering team through to release.
Build small features and customisations needed for specific merchant setups — from the change itself through testing and rollout.
Write and maintain the tooling that makes all of the above faster: sample clients, diagnostic scripts, internal utilities.
Occasionally support the commercial team during a deal: answer a technical or security questionnaire, confirm whether a use case is supported, sanity-check a proposed integration approach.
Who We Are Looking For
Two profiles work equally well here, and we are open on seniority:
A developer early in their career who would rather solve real customer problems than sit behind a backlog — and who is comfortable being the one talking to the merchant.
An experienced support or integration engineer who already owns customer-facing technical problems and writes code to solve them, not just tickets about them.
Required Skills and Qualifications
Coding: You write Java comfortably and can work inside an existing codebase — read it, change it, test it, ship it.
Working with AI: You already work with an AI coding harness (Claude Code, Codex or similar) and reach for it daily — to get through a stack you have not seen before, to draft a fix, to move faster. This is not a bonus point here. It is how the team works, and we expect you to arrive already working this way.
Reading other people’s code: Merchants integrate in whatever they use. You can follow unfamiliar code well enough to find the bug in it. Python, Node or other languages are a plus.
Debugging: Proven ability to diagnose problems in running systems — reading logs, following a request across services, forming a hypothesis and proving it. This is the core skill of the role.
APIs and integrations: Practical understanding of REST APIs, authentication and signing, webhooks and callbacks, idempotency, and common integration failure modes.
SQL: You write your own queries to investigate production data.
Architecture: Solid grasp of client-server architecture, SaaS platforms and cloud conventions. AWS is a plus.
Tools: Postman, a DB client, an OpenAPI tool, Git.
English, written and spoken: You can explain a technical cause clearly to a non-technical colleague — in writing and on a call — without making them feel stupid. Most of this role happens in text, and the rest happens live with merchants and colleagues.
Nice to Have
Experience in payments, fintech, or another regulated domain.
Background in technical support, integration engineering, or professional services at a product company.
Experience improving how support works: tooling, templates, self-service documentation.
Practicalities
On-site in Belgrade, standard business hours on Belgrade time (roughly 9:00–17:00).
No on-call.
Merchants across Europe and Africa.
English is the only working language — with merchants, with Account Managers, internally.
Published on: 9/21/2026
Unlimit
Unlimit is a cross-border payments company that works with e-commerce merchants, offering payment gateway services and acquiring for online stores, high-risk businesses and an on&off-ramp fiat solution for crypto, DeFi, and GameFi.
We operate both locally and internationally with ease across Europe, the UK, LATAM, APAC, India, and Africa.
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