production Java services and RESTful APIs (Spring Boot or similar), designed for integration by multiple consuming systems and documented to OpenAPI Design and implement MongoDB document models, aggregation pipelines, indexing and sharding strategies, and integrate them cleanly into Java service layers rather than through a leaky abstraction Build data pipelines … streaming ingest, transformation frameworks, checkpointed batch extract workers, and MongoDB sink configuration and tuning at terabyte scale Implement access control, encryption and audit within the application and data layer, including enforcement inside the MongoDB query path, rather than bolted on around it Write the tests: unit, integration, golden-record fixtures ...