Senior Python Full-Stack Developer (Python+React)

Overview Project description: We have an ambitious goal to migrate a legacy system written in HLASM (High-Level Assembler) from the mainframe to a cloud-based Java environment for one of the largest banks in the USA.

Responsibilities

We are looking for an experienced Senior Python Developer who can help perform the migration of the client platform:

Troubleshoot, debug, and resolve issues in GenAI-powered code translation pipelines

Collaborate with dev and client teams to ensure alignment with project goals and deliver high-quality solutions

Maintain and fine-tune RAG application that supports the migration process, specifically optimizing LLM prompts for pattern recognition

Build and maintain FastAPI-based microservices that orchestrate the migration workflow

Implement RAG (Retrieval Augmented Generation) systems using LangChain /Langgraph/LlamaIndex for contextual code understanding

Design stateful migration workflows using LangGraph/LangChain/LlamaIndex for complex multi-step transformations

Mandatory work from the office 5 days per week

Skills Must have

Experience in front-end development (preferably React) for building migration dashboards and progress monitoring interfaces (2+ years)Proficiency in Python development (5+ years), with specific expertise in:

FastAPI for building high-performance REST APIs and WebSocket connections

Async programming patterns for handling concurrent migration tasks

Pydantic for robust data validation in migration pipelines

Experience with vector embeddings and embedding models

Vector database implementation for semantic search

Graph database experience for code dependency mapping

Building agents for code analysis, implementing custom tools for mainframe-specific transformations, creating chains for multi-step code migration

Orchestrating stateful workflows for complex migration scenarios, managing checkpoints for long-running migrations, implementing conditional routing based on code patterns

Building knowledge bases from documentation, implementing hybrid search for code pattern matching, creating custom retrievers for language specific contexts

Implementing similarity search and semantic code retrieval systemsGraph traversal algorithms for dependency analysis

Strong problem-solving and debugging skills for identifying translation anomalies and semantic preservation issues

Excellent communication skills for collaboration with client teams and explaining complex technical translations

Nice to have

• Deep understanding of HLASM instruction sets, macro definitions, and DSECT mappings • COBOL and PL/I for understanding integrated mainframe systems • Assembly language debugging and performance optimization • Mainframe utilities (DFSORT, IEBGENER, IDCAMS) • Experience with mainframe subsystems: CICS transactions, DB2 stored procedures, JCL batch processing • Knowledge of z/OS internals, linkage conventions, and program calling standards • Familiarity with EBCDIC to ASCII conversion, packed decimal (COMP-3) handling • Experience in Java development, particularly Spring Boot, to understand target architecture requirements • Familiarity with large-scale system migrations and modernization efforts, including phased migration strategies and dual-run validation • Prior experience working in the banking or financial services industry, understanding core banking concepts, regulatory requirements, and transaction processing • Knowledge of performance tuning and optimization in cloud environments, including auto-scaling strategies and cost optimization

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