Order Fulfillment System Low-Level Design
What is Order Fulfillment? Order fulfillment covers the steps from a confirmed order to the item delivered to the customer: […]
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Inventory Management System Low-Level Design
Requirements Track stock levels across multiple warehouses for millions of SKUs Reserve inventory when an order is placed; deduct when
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Referral System Low-Level Design
Requirements Users share a unique referral code or link to invite new users Referrer earns a reward when a referred
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DNS Resolver and DNS System Design
What Does a DNS Resolver Do? The Domain Name System (DNS) translates human-readable domain names (www.example.com) into IP addresses (93.184.216.34).
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Chat System Low-Level Design (WhatsApp / Messenger)
Requirements One-on-one and group messaging (up to 500 members) Message delivery with read receipts (sent, delivered, read) Message history persistence
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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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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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Feature Store System Low-Level Design
What is a Feature Store? A feature store is a centralized repository for ML features. It solves the “feature engineering
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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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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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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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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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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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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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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