Covers writing clean, maintainable, and readable code together with proactive techniques to prevent failures and handle unexpected inputs. Topics include naming and structure, modular design, consistent style, comments and documentation, and making code testable and observable. Defensive practices include explicit input validation, boundary checks, null and error handling, assertions, graceful degradation, resource management, and clear error reporting. Candidates should demonstrate thinking through edge cases such as empty inputs, single element cases, duplicates, very large inputs, integer overflow and underflow, null pointers, timeouts, race conditions, buffer overflows in system or embedded contexts, and other hardware specific failures. Also evaluate use of static analysis, linters, unit tests, fuzzing, property based tests, code reviews, logging and monitoring to detect and prevent defects, and tradeoffs between robustness and performance.
EasyTechnical
25 practiced
Describe the role of assertions and invariants in maintaining code correctness. When should assertions be used versus throwing exceptions? Provide an example where assertions detect developer errors early and avoid costly runtime checks in production.
HardTechnical
24 practiced
After a production outage caused by a release that passed CI, outline a structured postmortem that focuses on root cause, contributing factors, action items, and measurable prevention. Describe how to use test artifacts, canary data, dashboards and tracing to surface the failure earlier next time.
MediumSystem Design
24 practiced
Design an automated test pipeline for a web application that includes unit tests, integration tests, end-to-end tests, security fuzz tests, and performance regression tests. Specify stages, environments, test-data management, parallelization, flakiness mitigation, and strategies to keep the pipeline fast and reliable.
HardTechnical
28 practiced
Implement a thread-safe bounded queue in Java without using java.util.concurrent classes. Support enqueue, dequeue with optional timeout, and a shutdown method that unblocks waiters. Describe how you avoid race conditions, prevent deadlocks, and how you'd test correctness under contention.
HardTechnical
31 practiced
You're developing firmware for an IoT device that sometimes loses power mid-write and ends up with corrupted state. Describe defensive strategies at the software/firmware level to ensure state consistency and recovery: journaling, atomic writes, checksums, transactional updates, wear-leveling, and graceful degradation when state cannot be repaired.
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