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.

EasyTechnical

0 practiced

In Python, describe the difference between list comprehensions and generator expressions. For a streaming ETL job processing millions of rows, which should you use and why? Provide small code examples that illustrate memory behavior differences.

HardTechnical

0 practiced

Given a service that writes business data to a transactional relational database and also publishes events to an asynchronous analytics sink (Kafka), design a reliable approach that avoids data loss and limits duplicates. Explain the transactional outbox pattern, CDC approaches (Debezium), and idempotent consumers. Provide pseudocode for writing the outbox and for a publisher that guarantees at-least-once delivery with idempotent consumer semantics.

HardTechnical

0 practiced

Write a Python program outline for external merge sort to sort a 100GB newline-delimited file of integers on a machine with 8GB RAM. Describe how to choose chunk size, create on-disk sorted runs, perform a k-way merge (heapq.merge), manage temp files, and tune I/O buffering to maximize throughput. Include pseudocode focusing on memory and I/O constraints.

HardTechnical

0 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

0 practiced

Describe best practices for error classification and handling in backend ETL services (choose Java or Python). Cover retry policies (idempotent vs non-idempotent), exponential backoff, poison message handling, logging context without leaking secrets, and mapping failure types to alerting thresholds.

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