Senior / Staff Software Engineer (New Product) - Greenstep Espoo

Greenstep Sverige AB; Espoo; On-site; EUR 120,000 - 180,000; Full time

Job summary

Greenstep Sverige AB is assembling a small, senior team to build a new multi-tenant SaaS product from day zero. The stack is Go for core services, Python for AI and reporting, and React/TypeScript on the frontend, with Postgres and event-driven architecture. The role is hands-on and demands architectural ownership and strict quality.

Details will be shared in conversations. You will work closely with a compact, senior group and contribute to the product's design, data residency, and tenant

Qualifications

• Senior Staff Software Engineer with hands-on responsibilities.
• Own the architecture and define service boundaries for a new multi-tenant SaaS product.
• Emphasizes correctness, testing, and code reviews as non-negotiables.

Responsibilities

• Own the architecture of the system and define the boundaries between services and failure models.
• Design and build services end-to-end across Go core and Python layer.
• Own the multi-tenancy model including tenant isolation and data residency.
• Define the data layer's long-term strategy and scaling considerations.
• Use AI coding agents daily and maintain code quality.

Skills

Go

Python

React

TypeScript

PostgreSQL

Software architecture

Testing & reviews

AI tooling

Job description

Do you want to build something new from the first commit, with people who hold the bar as high as you do? We are a small senior team building a new product that has not been announced yet, and we are looking for one more engineer at the same level.

Greenstep is a Finnish, family-owned growth company founded in 2010 that provides high-quality technology and back-office services to support its clients' growth and success. Today we are a community of more than 800 experts working in the Nordics and across Europe. We have grown organically, and today Greenstep has people in Finland, Åland, Sweden, Norway, Estonia, Denmark and the Netherlands. We share one goal: to help growth companies become leaders in their fields.

Alongside our services we build our own software. BI Book already serves thousands of clients in several countries, Bezala 100t+ active users and several other good success stories. Now we are building our next product, and we are hiring the people who will build it.

The Role

You join a small team building a new multi-tenant SaaS product from day zero. We cannot say much publicly yet. We will tell you everything in the first conversation. What we can say now:

• The stack is modern and deliberate. Go for the deterministic core, Python for AI and reporting services, React and TypeScript on the front end, Postgres with row-level security underneath, and an event-driven architecture.

• We are spec driven. Every feature gets a product spec and a build spec before code. Schema changes ship with documentation. Decisions become architecture decision records.

• Correctness is non-negotiable. The product works in a domain where every change must be exact and auditable. Tests and reviews are not optional.

• AI is part of the workflow. You will use AI coding agents every day and hold their output to the same standard as any other code. As a Staff Software Engineer you will:

• You will own the architecture of the system, not just the services in it. You set the boundaries between services, the contracts between them, and the failure model that holds when one of them is down.

• You'll design and build services end to end, from schema to API to tests to production, across the Go core and the Python layer. This is a hands-on role and stays hands-on.

• You will own the multi-tenancy model. Tenant isolation, data residency, noisy-neighbour behaviour and the blast radius of any single tenant are your call, and you make that call explicit in writing.

• Own the data layer's long game. Schema design, partitioning strategy, and a defensible answer to when the system needs to scale horizontally and what it costs when it does.