Senior .NET Backend Engineer - FIX Protocol (FinTech)

Avenga; Polska; Hybrid; PLN 180,000 - 320,000; Full time

Job summary

Avenga seeks a strong backend engineer in Poland for a FinTech-focused role. You will design and build scalable microservices using .NET, MongoDB, Redis, RabbitMQ, Pulsar, and Elasticsearch, collaborating in a 7-person team with exposure to React frontend.

You should have 5+ years in backend, deep C#/.NET, APIs, distributed messaging, FIX protocol experience in capital markets, and finance-related modeling with QuantLib. This is hands-on and high-impact.

Qualifications

• 5+ years of backend development experience.
• Strong C#/.NET and API design expertise.
• Experience with distributed messaging systems and event-driven architectures.
• FIX protocol experience in capital markets or electronic trading.
• Knowledge of financial calculations, pricing engines, or quantitative models.
• Hands-on with QuantLib or similar libraries.
• OAuth2 / OpenID Connect authentication experience.
• Experience with MongoDB or other NoSQL databases.
• Exposure to capital markets, fintech, trading platforms, or fixed income.

Responsibilities

• Design and develop high-quality backend services using C#/.NET.
• Build scalable ASP.NET service-side applications with reliability.
• Work with distributed messaging frameworks and event-driven architectures.
• Develop and optimize data solutions using NoSQL databases like MongoDB.
• Design and implement financial calculation engines and pricing models.
• Implement FIX protocol integrations for electronic trading workflows.
• Define identity and authorization solutions across backend services.
• Collaborate with product, frontend, and DevOps teams on deployment strategy.
• Mentor engineers and uphold coding standards.

Skills

Backend development

C#/.NET

API design

Distributed messaging

Event-driven architectures

FIX Protocol

Quantitative finance

QuantLib

OAuth2/OpenID

MongoDB

Capital markets

Tools

MongoDB

Redis

RabbitMQ (MassTransit)

Pulsar

Elasticsearch

Datadog

Sentry

React

Redux

Job description

Avenga seeks a strong backend engineer in Poland for a FinTech-focused role. You will design and build scalable microservices using .NET, MongoDB, Redis, RabbitMQ, Pulsar, and Elasticsearch, collaborating in a 7-person team with exposure to React frontend.

You should have 5+ years in backend, deep C#/.NET, APIs, distributed messaging, FIX protocol experience in capital markets, and finance-related modeling with QuantLib. This is hands-on and high-impact.