Senior Software Engineer — Security-First Fintech Scale-Up

Kultakiertue Oy; Helsinki; On-site; EUR 72,000 - 90,000; Full time

Benefits offered by this job

Unlimited AI tokens

Competitive salary

Career growth

Ownership of security

Supportive team

Job summary

Kultakiertue Oy, a Helsinki-based scale-up, seeks a hands-on Senior Developer to join our in-house engineering team. You will build secure, mobile-first web apps using SvelteKit, Node.js, TypeScript and PostgreSQL, shaping architecture and data flows across our platform.

You will own security in day-to-day development, implement access controls, handle personal and financial data safely, and collaborate on compliance reporting as we expand into new markets.

Qualifications

• Proven track record building complex, mobile-first web apps (Svelte/SvelteKit or similar).
• Strong experience in backend and/or frontend development (Node.js, TypeScript, React, Vue or similar).
• Solid database and integration skills (PostgreSQL, REST APIs, row-level security a plus).
• A security-first mindset: you think about authentication, authorization, PII handling and the OWASP Top 10 as part of normal development.

Responsibilities

• Develop new features and integrations across our internal apps (routes, bookings, payments, etc.).
• Help with planning and managing country-specific compliance and reporting requirements.
• Own security in day-to-day development: access control, secure handling of personal and financial data, and safe integration patterns.
• Contribute to secure architecture and technology decisions, including threat modeling, testing, code review, and dependency and secrets hygiene.
• Build and maintain integrations.
• Monitor and optimize workflows, data quality and system reliability.
• Support broader IT and software needs across the company.

Skills

SvelteKit

Node.js

TypeScript

PostgreSQL

REST APIs

Security mindset

Data protection

Startup experience

English fluent

Tools

Vercel

Supabase

Job description

Kultakiertue Oy, a Helsinki-based scale-up, seeks a hands-on Senior Developer to join our in-house engineering team. You will build secure, mobile-first web apps using SvelteKit, Node.js, TypeScript and PostgreSQL, shaping architecture and data flows across our platform.

You will own security in day-to-day development, implement access controls, handle personal and financial data safely, and collaborate on compliance reporting as we expand into new markets.