Backend Language Proficiency Questions

Demonstrate strong practical knowledge of a backend programming language such as JavaScript with Node dot js, Python, Java, Go, or similar. Cover language fundamentals, idiomatic usage, standard library features, package and dependency management, common frameworks and ecosystem tools, testing strategies and tooling, error handling and observability, and patterns for maintainable server side code. Be ready to explain concurrency and asynchronous models in the language, performance considerations, security best practices, deployment and packaging approaches, and examples of backend services or APIs you built including trade offs and chosen libraries.

MediumTechnical

42 practiced

You inherited a legacy Node.js ETL codebase full of callback-based modules and technical debt. Propose an incremental refactor plan to adopt async/await and modular patterns without breaking production. Include testing, feature flags, canary rollout, and a strategy for developer training and code review to prevent regressions.

HardTechnical

37 practiced

A Node.js ETL service shows increasing memory over time indicating a leak. Describe how to diagnose Node memory leaks: collect heap snapshots with --inspect, use Chrome DevTools or clinic/heapdump, analyze retaining paths, and fix common patterns (unbounded caches, forgotten event listeners). Provide example code of a leaking pattern and corrected code.

MediumTechnical

40 practiced

Provide a sample multi-stage Dockerfile for a Java 17 Spring Boot microservice that builds with Maven and produces a minimal runtime image. Include JVM tuning environment variables suitable for a memory-limited container, and explain why multi-stage builds reduce image size and improve reproducibility.

HardSystem Design

34 practiced

Design a zero-downtime deployment strategy for a stateful Java caching service that holds in-memory caches. Consider blue/green, rolling with draining, cache warming, client-side retries, in-flight requests, and data format migrations. Provide a step-by-step plan to deploy a change that alters cache format without taking the system offline.

EasyTechnical

38 practiced

Explain immutable vs mutable data structures and why immutability can help in concurrent backends. Give examples in Python and JavaScript of bugs immutability avoids and discuss trade-offs in memory and performance when choosing immutable structures in transformation code.

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