Guides
Guides for System Design, DSA and Design Patterns
Short, plain-English guides that answer the questions people search for, with links into the interactive lessons.
How to Prepare for a System Design Interview: An 8-Week Plan
A week-by-week plan to prepare for a system design interview: what to learn, in what order, a 45-minute framework, and the mistakes that cost the most.
7 min readHLD vs LLD: What Is the Difference?
HLD (system design) and LLD (object-oriented design) compared with a table and a parking-lot example, plus what to study first for interviews.
5 min readLatency Numbers Every Engineer Should Know
Approximate latency numbers for memory, SSD, disk and network, plus powers of two, uptime nines and quick estimation tricks for system design.
6 min readLeetCode Patterns: 14 Patterns That Cover Most Interview Problems
The main LeetCode patterns (hashing, two pointers, sliding window, binary search, trees, heaps, backtracking, DP and more), how to recognise each, with practice problems.
7 min readDesign Patterns Cheat Sheet: When to Use Each of the 23 Patterns
A one-line summary of every classic design pattern (creational, structural, behavioral) and the SOLID principles, each linked to a lesson with a diagram and code.
5 min readSQL vs NoSQL: How to Choose a Database
A practical way to choose between SQL and NoSQL databases: access patterns, consistency, scale, the four NoSQL families, and what to say in an interview.
6 min readCaching Strategies Explained: Cache-Aside, Write-Through and Write-Back
The main caching strategies and eviction policies, when to use each, and the problems to plan for: stale data, cache stampede and missing keys.
6 min readCAP Theorem Explained Simply
What the CAP theorem really says, why partition tolerance is not optional, examples of CP and AP systems, and how quorums and PACELC fit in.
5 min read