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.

HardTechnical

35 practiced

Design a small experiment and write the code (or pseudocode) to compare two JSON libraries in your language for speed and memory allocation when serializing a representative payload. Explain how to run the benchmark reliably, which metrics to collect, and how to interpret variance in results.

HardSystem Design

43 practiced

Design a language-agnostic approach (and show one example in your language) for safely loading and applying runtime configuration updates to a backend service without restarting. Include atomicity guarantees, validation, and rollback strategy if the new config causes errors.

MediumTechnical

33 practiced

Write a small implementation of an LRU cache in your chosen backend language (Python, Go, Java, or Node.js) with O(1) get and put operations. The cache should support a maximum capacity and evict the least recently used item when full. Provide idiomatic comments about concurrency safety if the cache will be used by multiple threads/goroutines/event-loop workers.

EasyTechnical

44 practiced

Explain, in concrete terms, the difference between synchronous blocking I/O and asynchronous/event-driven I/O in backend languages (choose one to illustrate: Python, Node.js, Java, or Go). Provide one concise example of idiomatic code for the chosen language that demonstrates asynchronous I/O and explain why it improves throughput under high concurrency for I/O-bound workloads.

EasyTechnical

62 practiced

Provide a concise checklist of secure coding best practices you would follow when writing backend services in your language. Include items related to secrets handling, dependency vetting, input/output validation, safe serialization/deserialization, and runtime hardening. Give one short code example of secret retrieval that avoids embedding secrets in source.

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