Application Engineering Senior Developer

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 unders