Senior Backend Engineer - Payments & Billing (AWS, TypeScript)

Spirii; København; On-site; DKK 900,000 - 1,200,000; Full time

Benefits offered by this job

Flexible Working Hours

Competitive Salary & Benefits

32 paid vacation days

Job summary

Spirii is seeking a Senior Backend Software Engineer to join the Payments team in Copenhagen. You will lead development of scalable, secure backend services and cloud-native pipelines, focused on data ingestion, invoicing, and payouts within a financially sensitive codebase.

You will own architecture, mentor engineers, and collaborate with Finance and partner teams, while leveraging AI-assisted workflows to boost productivity and ensure data integrity.

Qualifications

• Bachelor's degree in Computer Science, Software Engineering, or a related field (or equivalent experience).
• 7+ years of professional software development experience.
• Extensive hands-on experience designing and scaling production backend systems, including event-driven, queue/job-based architectures.
• Strong experience building TypeScript or JavaScript (Node.js, NestJS) microservices on cloud platforms such as AWS.
• Experience leading design discussions, mentoring engineers, or acting as a technical point of contact for a team or domain.
• Hands-on experience with test-driven development, test automation, integration and load testing.
• Strong SQL and data-modelling skills, with the discipline needed for financially accurate, auditable data.
• Experience integrating external and internal IT systems, and solid API design.
• Experience with developing secure software is a plus.
• Knowledge of Redis and NoSQL databases is an advantage.
• Experience working with or integrating ERP systems (e.g. Microsoft Business Central) is an advantage.
• Experience with billing, payments, invoicing, or other financial/transactional systems is a strong plus.
• Hands-on experience using AI assistants and/or agentic workflows to improve engineering productivity is a plus.

Responsibilities

• Designing, building, and maintaining scalable, secure backend services and cloud-native queue-based pipelines (Node.js, NestJS, TypeScript) that power data ingestion, processing, and invoice generation at high throughput.
• Ensuring data quality through correct aggregation and safe handling of late or updated records.
• Building and maintaining integrations with internal services and our ERP system.
• Significantly contributing to architectural decisions and solution design for cloud-native, distributed, event-driven systems on AWS.
• Driving automated testing and observability to protect billing correctness and catch data discrepancies early.
• Mentoring other engineers and raising the technical bar of the team through code review, pairing, and constructive feedback.
• Operating independently on ambiguous, cross-team problems with minimal oversight.
• Using AI coding assistants and agentic workflows to accelerate development and automate repetitive tasks while helping the team adopt AI safely in a financially sensitive codebase.

Skills

Strong English communication

Cloud tooling mindset

Education

Bachelor's degree in Computer Science or related field

Tools

Node.js

NestJS

TypeScript

AWS

SQL

Redis

NoSQL

ERP systems

Billing/payments experience

Job description

Spirii is seeking a Senior Backend Software Engineer to join the Payments team in Copenhagen. You will lead development of scalable, secure backend services and cloud-native pipelines, focused on data ingestion, invoicing, and payouts within a financially sensitive codebase.

You will own architecture, mentor engineers, and collaborate with Finance and partner teams, while leveraging AI-assisted workflows to boost productivity and ensure data integrity.