Implement a REST Endpoint That Aggregates Data from Multiple Internal Services

Late January, 2026

The interviewer asked me to design and implement a backend REST API endpoint that aggregates data from multiple internal services into a single response. The core requirement was to build a GET /api/bootstrap endpoint that accepts a user_id and returns consolidated information from three internal domains: Consumer data (consumer ID and roles) Address data (formatted address including name, street, city, state, and ZIP) Payment data, including: Default payment card details (last four digits, expiration month/year, fingerprint, created date) Aggregated available gift card credits Key constraints and expectations mentioned or implied during the interview: The endpoint must call multiple internal services (Consumer, Address, Payments) and aggregate the results into a single response. Each internal service could fail independently, so the solution needed basic error handling and clear response behavior. The response should include only production-ready fields — any debug or internal-only fields must not be exposed. The interviewer was more focused on API design, data modeling, and aggregation logic than on framework-specific details. Clean structure, readability, and reasonable assumptions were more important than completing every edge case. The task was time-constrained, and correctness of approach and reasoning mattered more than perfect implementation. Overall, the question tested system design thinking at a small scale: how to orchestrate multiple services, define a clean contract, and return a coherent API response under realistic backend constraints.

Mid September, 2025

Combine responses from multiple services with happy and error paths