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Introduction: System design can feel overwhelming — especially when vast topics like scalability, performance, reliability, and distributed architecture are thrown at you all at once. But once you master the foundational building blocks, designing robust and scalable systems transforms from stressful to doable. In this post, we’ll explore 30 essential system design concepts with explanation 1. Client–Server Architecture What it is: The foundational model: thin clients (browsers, mobiles, IoT) make requests; servers process logic and return responses. Servers can be single or a pool of machines. Why it matters: It separates concerns — UIs live in clients and heavy computation/state in servers — enabling centralized control, security, and shared business logic. Trade-offs & details: Clients must handle availability issues and degraded connectivity. This model fits web apps, but for extreme scale you need caching, CDNs, and stateless servers (see Diag...

Introduction In multi-threaded Java applications, managing shared data safely and efficiently is crucial. Two common approaches are using Synchronized HashMap (via Collections.synchronizedMap(...) ) and ConcurrentHashMap . While both aim to provide thread-safety, their implementations and performance characteristics differ significantly. This post explores these differences in detail. What is a Synchronized HashMap? Created by wrapping a regular HashMap using: Map<K, V> syncMap = Collections.synchronizedMap(new HashMap<>()); Enforces synchronization at the object level , meaning only one thread can access the map at any time (read or write). Supports null keys and values since it relies on HashMap behavior. Iterators are fail-fast , throwing ConcurrentModificationException if the map is modified while iterating. Simpler implementation, suitable when concurrency is low or performance is not cri...