Who we are

Montis Labs is a fintech engineering company building the infrastructure behind modern banking and payment products.

We are developing Montis, a modular, API-first financial platform covering core banking, payments, FX, compliance, and financial operations. At its foundation is a real-time, double-entry ledger designed to provide a consistent and auditable source of truth across the platform.

We build systems where correctness, traceability, security, and reliability are fundamental requirements.

Our engineers work across the stack and are expected to understand how a feature behaves end-to-end: from the user interface and API contract to business logic, database design, messaging, and integrations with financial infrastructure.

We are a small, engineering-driven team, which means developers have significant ownership and influence over architecture and technical decisions. We value pragmatic engineering, clean system design, strong typing and testing, and people who are comfortable understanding the system beyond the code immediately in front of them.

We are also actively exploring how AI-assisted development and software engineering agents can improve the way production-grade financial software is designed, built, tested, and maintained.

Learn more at http://montis.systems

General Profile

We are looking for full-stack engineers with strong end-to-end ownership who are comfortable working across the entire application stack: frontend, backend, APIs, databases, messaging, and integrations.

Beyond proficiency with our technology stack, we expect engineers to understand how a feature works as a complete system: from the user interaction and API contract to the underlying business logic, data model, asynchronous processes, and audit trail.

In fintech, correctness and traceability are non-negotiable. We therefore value engineers who understand how their code fits into the broader system rather than specialists who operate exclusively within a single layer.

In practice, this means being comfortable:

• Reading, designing, and contributing to database schemas, not simply consuming APIs.
• Understanding how frontend decisions affect API contracts, business logic, and data models.
• Following a transaction or business process across multiple services and system boundaries.
• Diagnosing issues anywhere in the stack rather than immediately handing them off to another team.
• Thinking carefully about data integrity, concurrency, failure scenarios, auditability, and security.

Experience in banking, fintech, payments or other regulated environement is a strong advantage.

Web Application Engineer

The Web Application Developer will work across our customer-facing and operational applications, building interfaces that interact directly with Montis APIs and financial infrastructure.

We are looking for engineers who care about both the quality of the user experience and the integrity of the systems behind it.

Frontend

• React 19 + TypeScript in strict mode
• Tailwind CSS + Radix UI component primitives
• React Hook Form + Zod for form validation
• react-i18next for internationalisation
• AG Grid Enterprise for complex financial and operational data tables
• Chart.js / react-chartjs-2 for data visualisation
• Vite build toolchain
• Testing Library + Jest

Backend

• NestJS 11.x
• REST APIs and WebSockets via Socket.io
• MikroORM 6.x on PostgreSQL
• RabbitMQ using amqplib / amqp-connection-manager
• Keycloak integration using JWT / Passport
• Swagger / OpenAPI
• Jest + Supertest for integration testing

General Engineering

• TypeScript 5.7+ in strict mode
• ESLint 9.x + Prettier
• Strong understanding of API contracts and data modelling
• Ability to investigate issues across frontend, backend, and database layers
• Fintech / neobank domain knowledge is a plus

Core Banking System Engineer

The Core Banking System Developer will work on the systems responsible for financial operations, account and transaction processing, integrations, auditability, and other critical components of the Montis platform.

This role requires particular attention to correctness, data integrity, security, and failure handling.

Core

• NestJS 11.x, modular architecture, guards, interceptors, and decorators
• TypeScript 5.7+ strict — including decimal-safe monetary arithmetic and avoiding unsafe typing
• MikroORM 6.x, Unit of Work pattern, JSONB, and migrations
• PostgreSQL 16.x, multi-tenant schema design and JSONB audit logs
• Zod, runtime schema validation

Infrastructure & Integrations

• Redis 7.x — token blacklisting and TTL-based caching
• RabbitMQ 3.13+ — asynchronous message consumption and queue topology
• REST API integrations with third-party financial infrastructure
• Experience integrating payment, FX, banking, or financial service providers such as Convera or equivalent

Security

• JWT guard chains covering authentication → roles → tenant → permissions
• OAuth 2.0 client credentials flow
• Secure secret and configuration management
• No hardcoded credentials
• Sanitisation of logs, error messages, and audit trails
• Strong awareness of tenant isolation and access-control boundaries

Testing & quality

• Jest 29.x
• Strong emphasis on integration testing and real system behaviour rather than excessive unit mocking
• ESLint 9.x + Prettier 3.x
• class-validator for DTO validation
• Attention to failure scenarios, edge cases, and transactional consistency

Domain Experience

Experience in one or more of the following is particularly valuable:

• Payment processing
• SWIFT, including pacs.008 or equivalent payment messaging
• SEPA and other payment rails
• Banking / fintech infrastructure
• Multi-tenant SaaS architecture
• Immutable audit-log design
• Ledger and transaction-processing systems
• Reconciliation and financial data integrity

AI-Assisted Engineering

We believe AI is becoming part of the modern software engineering toolchain, and we are actively exploring how it can be used effectively in the development of production-grade financial systems.

We are interested in engineers who have experience with, or a strong interest in:

• Using Ai coding tools such as Claude Code, Codex, or equivalent as part of their development workflow.
• Using AI for code exploration, implementation, refactoring, debugging, testing, and documentation.
• Building effective workflows where AI assists engineers without compromising code quality, security, or understanding of the underlying system.
• Designing and using software engineering agents for more complex development tasks.
• Evaluating AI-generated code critically rather than treating generated output as inherently correct.

AI experience is valuable, but engineering judgement remains more important than the tool itself. In a financial system, developers remain responsible for understanding, reviewing, testing, and validating the software they ship.

What we value

Technology matters, but the way you approach engineering matters more.

We value people who:

• Own problems end-to-end.
• Understand the systems they modify rather than treating components as black boxes.
• Investigate before making assumptions.
• Care about correctness and maintainability.
• Think explicitly about failure modes and edge cases.
• Write code that other engineers can understand and safely modify.
• Use abstractions where they help, not simply because they can.
• Are comfortable challenging existing technical decisions when they can propose something better.
• Can move quickly without sacrificing control over critical financial logic.
• Use AI and automation to increase their effectiveness while retaining engineering judgement.

If you enjoy understanding complex systems, taking ownership of difficult technical problems, and building software where the details genuinely matter, we would like to hear from you.

The Senior Full-Stack Engineer role at Montis is a full-time, on-site position based in Bucharest, Romania.

In this role, the engineer designs, develops, and maintains both front-end and back-end features across core web applications, ensuring robust performance, scalability, and security.

Daily responsibilities include implementing user interfaces, building and integrating APIs, optimizing databases and server-side logic, and collaborating with product managers, designers, and other engineers to deliver high-quality solutions.

The engineer also reviews code, mentors team members, contributes to architectural decisions, and improves development processes and tooling. The role involves troubleshooting production issues, writing tests, and maintaining clear technical documentation.

Qualifications

• Strong Full-Stack Development and Software Development skills, with experience delivering complex web applications end to end.
• Proficiency in Front-End Development, including modern JavaScript frameworks and Cascading Style Sheets (CSS) for responsive, accessible interfaces.
• Solid Back-End Web Development experience, including building APIs, working with databases, and implementing secure, scalable server-side logic.
• Experience with version control systems (e.g., Git) and modern CI/CD pipelines.
• Comfort with agile development methodologies and collaborative team workflows.
• Ability to write clean, maintainable, and well-tested code, with strong debugging and problem-solving abilities.
• Effective communication skills and the ability to work constructively with cross-functional teams on-site in Vilnius.
• Bachelor’s degree in Computer Science, Engineering, or a related field, or equivalent practical experience.
• Experience with cloud platforms, containerization, or microservices architectures is beneficial.