Sr Backend Developer (C# / Typescript)

Backend Developer (C# / TypeScript) Location:

Valencia, Spain (Hybrid – 3 days/week in office near Torres de Serrano)

About Archie Join Archie, the AI agent built exclusively for accounting firms.

Archie isn't just another tool—he's a sophisticated digital team member who handles complex accounting workflows, from data consolidation to advisory services.

Our mission is to expand firms' capabilities by automating repetitive tasks while maintaining the highest standards of accuracy, security, and compliance.

Backed by industry veterans and partnering with top-tier accounting firms worldwide, we're building the future of accounting where human expertise meets cutting-edge AI technology.

At Archie, you'll join a team of forward-thinking professionals and passionate innovators who are committed to transforming how accounting firms operate.

Your work will impact thousands of accountants and their clients, shaping the evolution of AI in professional services.

The Role

We’re looking for a

Backend Developer

with strong experience in

C#

,

TypeScript

, and

PostgreSQL

to help us build, optimize, and scale our platform’s core services.

You’ll work closely with our AI engineers, data specialists, and frontend developers to deliver secure, high-performance APIs and integrations.

Our stack blends modern .NET and Node.js technologies, and we use AI-assisted tools (like Cursor and GitHub Copilot) to accelerate iteration and improve code quality.

Experience with

Semantic Kernel

or similar AI orchestration frameworks is a plus, as our architecture increasingly incorporates AI-driven task coordination and reasoning.

Responsibilities

Design and implement backend services in C# (.NET 8/9) and TypeScript (Node/NestJS).

Develop and maintain REST and GraphQL APIs used by internal and external clients.

Model and optimize PostgreSQL schemas, queries, and migrations.

Integrate with AI orchestration systems using

Semantic Kernel

and related frameworks.

Build integrations with AI inference services and data pipelines.

Write unit, integration, and performance tests to ensure reliability.

Collaborate with frontend and ML teams to ship features end-to-end.

Leverage AI-assisted development tools for faster prototyping and debugging.

Contribute to CI/CD pipelines and deployment automation.

Must-Haves

5+ years of professional backend development experience.

Strong proficiency in

C# (.NET Core or .NET 6+)

.

Proficiency in

TypeScript

and

Node.js

(preferably NestJS).

Proven experience with PostgreSQL

—including schema design, query optimization, and performance tuning.

Experience designing and consuming APIs. Strong focus on performance, security, and maintainability.

Fluent written and spoken English.

Schedule flexibility to be available until at least 6 PM CET for coordination with US-based teammates.

Nice-to-Haves

Experience with Azure (App Services, Functions, SQL, Storage, etc.).

Familiarity with Infrastructure as Code (Bicep/Terraform).

Experience with

Cosmos DB for PostgreSQL

or similar distributed Postgres systems.

Familiarity with

Semantic Kernel

or other AI orchestration frameworks.

Knowledge of message queues or background job systems.

Experience with AI/ML integrations or microservices.

Familiarity with GraphQL.

Knowledge of CI/CD pipelines (GitHub Actions, Azure Pipelines).

Experience using AI-assisted IDEs (Cursor, Copilot, etc.).

Hours:

40 hours/week, semi-flexible schedule (availability required until 7 PM CET).

Location:

Hybrid in Valencia, Spain (near Torres de Serrano); 3 days/week in office.

Compensation:

Competitive salary based on experience.