System Design Interview Preparation — Real-World Patterns by a Production Engineer
Good system design answers connect fundamentals to real product constraints: traffic, data shape, latency, consistency, failures, cost, and operational recovery.
Patterns Prabhat Uses in Real Systems
Prabhat's system design approach starts with requirements, APIs, data model, capacity estimates, component boundaries, failure modes, and trade-offs. HLD explains the system shape; LLD clarifies classes, interfaces, state transitions, and edge cases.
Rate limiting with Redis token buckets
Caching with explicit invalidation strategy
Sharding by tenant, user, or instrument
CAP theorem trade-offs for real workflows
Practical Examples
A trading system prioritizes real-time data, risk checks, idempotent order placement, and audit logs. An outreach platform prioritizes queue-based workflows, deduplication, sender reputation, reply classification, and analytics.
Requirements -> APIs -> Data Model -> Capacity Capacity -> HLD Components -> Failure Modes Failure Modes -> LLD Contracts -> Trade-offs
Rate Limiter Example
Rate limiting protects APIs from abuse and stabilizes downstream services during bursts. Redis is commonly used because counters and expiry operations are fast and centralized.
boolean allowRequest(String userId) { String key = "rate:" + userId; Long count = redisTemplate.opsForValue().increment(key); if (count == 1) { redisTemplate.expire(key, Duration.ofMinutes(1)); } return count <= 100;}Work with Prabhat
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