senior back end developer | tax technology consulting

At Deloitte, the spirit of excellence is part of our DNA. We strive to hire the brightest minds from all around the globe, allowing us to excel in both long-term strategic thinking and business improvement implementation as the undisputed global leader in professional services. We are committed to delivering impacting results for diverse private and public organization clients, linking our peerless talent in audit with unrivaled opportunities for impact – committing ourselves to sustainable growth and investment in our employees’ development and inclusion along the way.

Since 2018, Deloitte has been operating its Competence Center in Thessaloniki with satellites in the cities of Patras, Heraklion, and Ioannina - which are model hubs of expertise, training, and innovation, specializing in cutting-edge exponential technologies, in which graduates and young professionals undergo immersive experiences, continuous learning, gaining practical insights and hands-on training that empower them to navigate the complexities of the digital landscape.

Deloitte is an ideal working environment for both young and senior professionals who want to take the next step in their careers, offering them a supportive and international working environment that leverages their expertise and potential. Its corporate culture is based on trust and collaboration and ensures diversity and inclusion so that everyone feels part of a great team.

Due to our continuing expansion, we are currently seeking ambitious team players with exceptional analytical skills and a well-rounded personality to become part of our dynamic and highly motivating Tax & Legal practice in Thessaloniki.

#YourServiceLine

Tax & Legal

As global forces fundamentally shift how the tax function operates, tax leaders must become strategic advisors. We collaborate closely with our clients, connecting them to expertise, capabilities, technology, and innovative ideas that enhance agility, enabling them to lead their businesses through complexity with confidence. KBVL, member of the Deloitte Legal international network, is an independent law firm registered with the Athens Bar, that offers legal services aligned with clients’ key business objectives.

#YourRole

As a Senior Consultant in our Tax Technology Consulting team, you will work as the Senior Backend Engineer and squad lead for our AI platform used across professional services.

The backend is built on FastAPI (Python) with multiple modules, services, and a comprehensive middleware stack. It connects to MongoDB, PostgreSQL, Redis, and Azure cloud services.

You will own the backend codebase — API layer, business logic, data layer, authentication and authorization. In addition, you will lead and mentor the backend squad, establish code quality standards, and serve as the quality gate for all backend changes.

#KeyResponsibilities

• Own the backend codebase — API routes, services, data access layer, middleware, and business logic.

• Lead the backend squad — code review, mentoring, task assignment, and quality standards.

• Design and maintain the data layer across MongoDB, PostgreSQL, and Redis.

• Own the authentication and authorization layer — Azure AD integration and role-based access control.

• Maintain and evolve real-time communication infrastructure — SSE streaming and WebSocket notifications.

• Build and maintain supporting services for data pipelines, scheduled jobs, and workflow orchestration.

• Design and implement database migrations, schema evolution, and data consistency strategies.

• Ensure API design consistency, versioning, and documentation standards.

• Collaborate with the AI team on integration points.

• Conduct thorough code reviews for all backend pull requests.

• Own backend performance — query optimization, caching strategy, and async request handling.

#RequiredSkills

To qualify for the role, you must have:

• Bachelor's degree in Computer Science, Software Engineering, or a related field.

• 3–6 years of professional backend engineering experience.

• Expert Python proficiency with production FastAPI experience, async programming, dependency injection, and API design.

• Deep experience with MongoDB (or similar) — schema design, aggregation pipelines, indexing strategies, and performance optimization.

• Solid PostgreSQL experience — relational schema design, migrations, and query optimization.

• Redis experience — caching patterns, pub/sub messaging, and distributed locking.

• Experience with code review and engineering mentorship.

• Understanding of async programming patterns — asyncio, concurrent request handling.

• Experience with RESTful API design, versioning, and documentation (OpenAPI/Swagger).

• Excellent written and verbal communication skills in English.

#PreferredSkills

• Experience with SaaS or platform architecture.
  Familiarity with Azure AD / Microsoft Entra ID authentication and RBAC patterns.

• Experience with WebSocket and Server-Sent Events (SSE) for real-time communication.

• Knowledge of Azure cloud services — Blob Storage, Key Vault, Application Insights.

• Experience building data pipelines, ETL processes, or workflow orchestration (e.g. Airflow, Celery, or equivalent).

• Understanding of AI/ML integration patterns.

• Familiarity with automated testing strategies — unit, integration, and end-to-end testing in Python.

• Experience with mentoring junior and mid-level backend engineers.

#WhatWeOffer

At Deloitte, we know that great people make a great organization. We value our people and offer employees a broad range of benefits.

• Modern hybrid workplace, characterized by flexibility and Smart Working

• Empowered well-being: We provide multiple program offerings to support your well-being needs (flexible working arrangements, extra days of leave, parental allowances)

• Engagement within international large-scale teams and projects, with opportunities to travel for training or client purposes.

• Constant opportunities for learning with unlimited access to internal and external learning platforms and sponsored certificates aligned with business needs and technology trends

• Challenging and innovating environment where personal development and growth are encouraged, always with transparency and trust

• Diverse culture and active communities that enable you to bring yourself to work

• Team Building and Corporate Social Responsibility Activities

• A buddy to support you with your onboarding

• Private medical health insurance plan

• Ticket restaurant card

• Exclusive Discounts to several retail providers, restaurants and others

• Mobile phone

• Fresh fruits and unlimited coffee everyday at our offices