Senior Kotlin Developer

Company: Flowlix (AI-native EMI, payment infrastructure for European merchants)

Location: EU countries, B2B contract. We can consider candidates with RF/RB passports provided they genuinely reside/pay taxes in the EU. We cannot consider candidates from RF and RB without EU residency due to strict regulatory requirements.

Salary range: from $5000 to $8000 gross

We are looking for a strong Senior Kotlin developer to join a team building a payment infrastructure from scratch: financial core (ledger, settlement, reconciliation), integrations with processing and payment gateways, webhook processing, BPMN processes (Camunda).

Stack: Kotlin, Spring Boot, PostgreSQL, event-driven architecture. The role is backend-heavy (~85% backend), but a willingness to occasionally handle small frontend tasks is required (React/Angular at a basic level - no deep expertise needed).

No legacy or bureaucracy, working in a small team directly with the CTO. We expect proactivity, high independence, and a genuine AI-first approach to work.

Requirements:

• 6+ years of commercial experience in Kotlin or Java (Spring Boot) - REST API, JPA/Hibernate, transactions;
• Basic understanding of modern frontend stack (React/Angular) - at a level of "can handle a small task", nothing more;
• PostgreSQL — queries, migrations, indexes, JSONB;
• REST API design — versioning, error handling, idempotency;
• Git, CI/CD;
• Experience with webhook processing and event-driven architecture;
• Okta / OAuth2 / OpenID Connect
• Active use of AI tools in development (Cursor, Codex, Claude Code) with a conscious approach to what is generated;
• Bonus points: experience in fintech/payments (ledger, settlement, reconciliation), understanding of double-entry bookkeeping, experience with Camunda/BPMN.

Contact for application: @sobolevavalery