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System Design · Question Set
Fundamentals & Principles interview questions for placements and exams.
Questions
13
Included in this set
Subject
System Design
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for System Design.
SRP reduces ripple effects. When a class owns one responsibility, changes are localized and easier to test. This improves cohesion and long-term maintainability. In system design, the same idea guides service boundaries: one clear capability per service keeps coupling low and evolution safer.
For complete preparation, combine this set with full subject-wise practice for System Design. You can also explore other subjects and sets from the links below.
Denormalize when read latency and complex joins dominate critical paths, or when pre-joined aggregates are repeatedly needed. It trims joins and can simplify queries. Risks include write amplification, anomalies, and harder integrity. You must add repair jobs, careful update paths, and validations to keep copies in sync.
Start with goals, scale, SLOs, and constraints. Define APIs, data model, and consistency needs. Sketch read/write flows with sequence diagrams and rough capacity estimates. Then address caching layers, storage choice, partitioning, replication, and failure handling. Close with trade-offs, cost, observability, and a phased rollout.
Derive modules, interfaces, and data transfer objects. Pick patterns (e.g., Strategy, Adapter) to isolate variability. Define class responsibilities and contracts per SOLID. Add sequence diagrams for critical flows, error handling, retries, and idempotency. Specify test seams and feature flags to release safely.
Sequence diagrams show lifelines and messages across participants with time flowing top to bottom. They’re ideal to explain request flows, retries, and timeouts in system design discussions.
High cohesion keeps related behavior together. Low coupling limits cross-module knowledge. This combo yields modules that are easier to change and scale independently.
Open–Closed says modules are open for extension, closed for modification. You prefer polymorphism, small adapters, or strategy objects. This reduces regression risk and supports A-B variants without invasive changes.
HLD frames the system: external contracts, data choices, consistency, partitioning, and resilience. LLD zooms into classes, patterns, and method-level details that realize those contracts.
Strategy separates what varies (algorithm) from the context using it. It improves testability and allows feature flags or per-tenant policies without branching everywhere.
Anchor on product impact: user tolerance for stale reads, regulatory needs, and failure stories. If latency and availability are king, prefer AP regions with conflict resolution and client-visible freshness markers. If correctness dominates (e.g., financial ledger), choose CP paths, accept higher latency, and invest in queues, retries, and user feedback for occasional write unavailability.
CAP states that under partition you trade serving every request (availability) against returning the latest consistent view (consistency). Designs pick AP or CP per workload and surface the guarantees to clients.
Services map to capabilities and can scale, release, and evolve independently. The trade-offs are operational complexity, network calls, and data consistency across boundaries.
TTL limits staleness automatically. Event invalidation updates or removes keys on data change. Choose eviction (LRU/LFU/FIFO) and consistency model per use case.