Dead Letter Queue (DLQ) System Low-Level Design
What is a Dead Letter Queue? A Dead Letter Queue (DLQ) holds messages that could not be processed successfully after […]
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System Design
Learn to design scalable, reliable systems that handle millions of users. System design interviews test your ability to architect real-world applications, considering tradeoffs, scalability, and best practices.
Core Topics:
Scalability: Load balancing, horizontal vs vertical scaling
Storage: Databases (SQL vs NoSQL), caching (Redis, Memcached)
Reliability: Replication, failover, disaster recovery
Performance: CDNs, caching strategies, database indexing
Common Design Questions:
Design URL shortener (bit.ly)
Design rate limiter
Design Twitter/Instagram feed
Design messaging system (WhatsApp)
Design file storage (Dropbox)
Interview Level: Senior engineers (L5+) at FAANG companies. Requires 3-5+ years experience to tackle effectively.
Preparation: Study system design patterns, understand distributed systems fundamentals, and practice mock interviews.
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Loyalty Program System Low-Level Design
Requirements Earn points on purchases and specific actions (sign-up, referral, review) Redeem points for discounts, rewards, or free items Tiered
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Event Sourcing System Low-Level Design
What is Event Sourcing? In a traditional system, the database stores the current state: “Account balance = $500.” In event
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Session Management System Low-Level Design
What is Session Management? Session management maintains the authenticated state of a user across multiple HTTP requests. HTTP is stateless
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Comment System Low-Level Design
Requirements Users can post comments on content items (posts, videos, products) Threaded replies (nested comments) up to N levels deep
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Cache System Low-Level Design (LRU, Write Policies, Redis Cluster)
Why Caching? A cache stores copies of frequently-accessed data in fast storage (RAM) to avoid expensive re-computation or round trips
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Email Delivery System Low-Level Design
Requirements Send transactional emails (password reset, order confirmation, notifications) and marketing emails (campaigns, newsletters) 100M emails/day, peak 10K/second during campaigns
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CI/CD Pipeline System Low-Level Design
What is a CI/CD Pipeline? CI (Continuous Integration): automatically build and test code on every commit. CD (Continuous Delivery/Deployment): automatically
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Secret Manager System Low-Level Design
What is a Secret Manager? A secret manager stores and distributes sensitive credentials (API keys, database passwords, TLS certificates, OAuth
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Log Aggregation System Low-Level Design
What is a Log Aggregator? A log aggregator collects logs from distributed services, normalizes them, stores them for search, and
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Rate Limiting System Low-Level Design (Token Bucket, Leaky Bucket)
Why Rate Limiting? Rate limiting protects services from abuse, ensures fair usage, and prevents cascading failures from traffic spikes. Applied
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Webhook Delivery System Low-Level Design
What is a Webhook? A webhook is a user-defined HTTP callback. When an event occurs in a platform (payment succeeded,
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Invoice and Billing System Low-Level Design
Requirements Generate invoices for subscriptions and one-time purchases Support multiple billing cycles: monthly, annual, usage-based Apply discounts, taxes, and proration
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Multi-Region Architecture Low-Level Design
Why Multi-Region? Single-region deployments fail entirely during a cloud provider AZ or region outage. Multi-region provides: (1) High availability —
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Search Suggestions (Autocomplete) System Low-Level Design
Requirements Return top-k (k=10) query suggestions as a user types, within 100ms Suggestions ranked by search frequency or relevance score