Application Engineering Senior Developer - .NET Full Stack & Integrations

Ernst & Young Advisory Services Sdn Bhd; Wrocław; Hybrid; PLN 240,000 - 360,000; Full time

Job summary

The Application Engineering Lead at EY GDS Poland is responsible for designing, building, and owning complex full stack applications and enterprise integrations. This role requires deep technical expertise across .NET, API integrations, databases, and data pipelines, with strong ownership of production systems, migration activities, and critical cutovers.

You will lead API integrations, front-end Angular work, SQL Server solutions, and ETL workflows in Azure Data Factory/SSIS, while mentoring

Qualifications

• 6+ years of experience in application engineering / full stack development with enterprise integrations.
• Experience in lead or senior technical roles with ownership of production systems.
• Experience supporting large migrations, platform transitions, or enterprise cutovers is desirable.

Responsibilities

• Lead API integrations using REST, JSON, OAuth2, JWT, and API keys.
• Lead front-end development using Angular/HTML/Typescript for enterprise apps.
• Design, implement, and maintain robust data integrations with error handling and logging.
• Own production systems and oversee migration waves and cutovers.
• Develop SQL Server solutions, with complex queries and performance tuning.
• Implement ETL/data pipelines using Azure Data Factory and/or SSIS.
• Ensure data accuracy, reconciliation, and governance across systems.
• Mentor engineers on integration patterns, coding standards, and best practices.

Skills

Angular

REST API

OAuth2

JWT

SQL Server

Azure Data Factory

SSIS

C#

.NET Core

Data Pipelines

UI Development

Education

Bachelor's degree in Computer Science

Tools

Angular

Azure Data Factory

SSIS

SQL Server

Job description

Application Engineering Senior Developer - .NET Full Stack & Integrations

Location: Wrocław - 2 days in office / 3 days remote

Let us introduce you the job offer by EY GDS Poland – a member of the global integrated service delivery center network by EY.

The opportunity

The Application Engineering Lead is responsible for designing, building, and owning complex full stack applications and enterprise integrations. This role requires deep technical expertise across .NET, API integrations, databases, and data pipelines, along with strong ownership of production systems, migration activities, and critical cutovers. The role operates with minimal supervision and serves as a key technical decision maker and escalation point.

Your key responsibilities

Application Development & Integrations

• Lead the design and implementation of API integrations using REST, JSON, and industry standard authentication mechanisms (OAuth2, JWT, API keys, etc.).
• Lead the design and Implementation of Front end applications using Angular/HTML/Typescript
• Build and maintain robust, secure, and scalable integrations with structured error handling, logging, and retry mechanisms.
• Design and implement reverse and batch integrations across internal and external systems.
• Act as the technical authority for complex integration patterns, data flows, and migration solutions.
• Design and develop SQL Server solutions, including complex queries, stored procedures, performance tuning, and indexing strategies.
• Perform production data fixes with strong governance, validation, and audit controls.
• Implement and manage ETL and data pipelines using Azure Data Factory (ADF) and/or SSIS.
• Handle large scale, high volume data processing, ensuring data accuracy, reconciliation, and integrity across systems.

Production Ownership & Reliability

• Own end to end accountability for critical production systems and integrations.
• Lead production issue triage, root cause analysis, and remediation, maintaining composure and sound judgment during high severity incidents.
• Serve as a trusted escalation point during production issues, migration waves, and release cutovers.
• Ensure system stability, observability, and operational readiness across environments.

Leadership & Stakeholder Management

• Operate independently with minimal guidance, making informed technical and delivery decisions.
• Act as a subject matter expert (SME) for integration and migration initiatives.
• Collaborate effectively with business stakeholders, architects, and delivery teams to translate requirements into technical solutions.
• Coordinate across multiple teams during migrations and production cutovers, ensuring aligned execution and clear communication.
• Mentor and guide engineers on integration patterns, coding standards, and operational best practices.

Supervision Responsibilities

• Direct reports
• Working relationships (daily) with EY ITSD and AMS Lead
• Working relationships (daily) with TCS AMS team
• Liaison to the Business for that Portfolio / App

Skills and attributes for success

Frontend & UI Engineering (Angular)

• Strong hands on experience with Angular (version 20+) for enterprise grade web applications.
• Experience designing and implementing component based architectures, reusable modules, and shared UI libraries.
• Strong understanding of Angular lifecycle hooks, dependency injection, routing, and state management.
• Experience with RxJS and reactive programming, including observables, subjects, and subscription management.
• Ability to consume and integrate REST APIs into Angular applications with proper error handling and retry logic.
• Experience implementing authentication and authorization mechanisms on the UI (token handling, role based access, guards).
• Proficiency in frontend performance optimization, change detection strategies, and lazy loading.
• Familiarity with responsive design and enterprise UI standards.
• Experience troubleshooting and resolving production UI issues with minimal supervision.

Core Technology Stack

• Strong hands on experience with .NET / .NET Core, C#, and full stack application development.
• Extensive experience with RESTful API design and integration, including:
• JSON payloads and schema validation
• Authentication and authorization mechanisms
• Structured error handling and resiliency patterns

Databases & Data Processing

• Advanced expertise in SQL Server, including:
• Stored procedures and performance optimization
• Controlled production data fixes
• Strong understanding of data reconciliation, validation, and high volume data handling.

ETL & Integration Platforms

• Hands on experience with Azure Data Factory (ADF) and/or SSIS.
• Knowledge of batch processing, scheduling, and dependency management.

To qualify for the role, you must have

• 6+ years of experience in application engineering / full stack development, with significant exposure to enterprise integrations.
• Prior experience in lead or senior technical roles with ownership of production systems.
• Experience supporting large migrations, platform transitions, or enterprise cutovers is highly desirable.

What we offer

EY Global Delivery Services (GDS) is a dynamic and truly global delivery network. We work across nine locations – Argentina, Hungary, India, the Philippines, Poland, Sri Lanka, Mexico, Spain and the United Kingdom – and with teams from all EY service lines, geographies and sectors, playing a vital role in the delivery of the EY growth strategy. From accountants to coders to advisory consultants, we offer a wide variety of fulfilling career opportunities that span all business disciplines. In GDS, you will collaborate with EY teams on exciting projects and work with well-known brands from across the globe. We’ll introduce you to an ever-expanding ecosystem of people, learning, skills and insights that will stay with you throughout your career.

• Continuous learning: You’ll develop the mindset and skills to navigate whatever comes next.
• Success as defined by you: We’ll provide the tools and flexibility, so you can make a meaningful impact, your way.
• Transformative leadership: We’ll give you the insights, coaching and confidence to be the leader the world needs.
• Diverse and inclusive culture:You’ll be embraced for who you are and empowered to use your voice to help others find theirs.

About EY

EY | Building a better working world

EY exists to build a better working world, helping to create long-term value for clients, people and society and build trust in the capital markets.

Enabled by data and technology, diverse EY teams in over 150 countries provide trust through assurance and help clients grow, transform and operate.

Working across assurance, consulting, law, strategy, tax and transactions, EY teams ask better questions to find new answers for the complex issues facing our world today.

In compliance with the requirements of the Whistleblower Protection Act, our company has established the Procedure for reporting breaches of law and undertaking appropriate follow-up actions. Any misconduct should be reported through the EY Ethics Hotline.

EY refers to the global organization, and may refer to one or more, of the member firms of Ernst & Young Global Limited, each of which is a separate legal entity. Ernst & Young Global Limited, a UK company limited by guarantee, does not provide services to clients.