原文：

System design is the process of defining the architecture, components, and interfaces of a system to satisfy specific requirements. Key principles include scalability, availability, and maintainability. Horizontal scaling adds more machines to distribute load, while vertical scaling upgrades existing hardware. A load balancer distributes incoming requests across multiple servers. Caching reduces database load by storing frequently accessed data in memory. Message queues decouple components and handle traffic spikes gracefully. Every design decision involves tradeoffs between cost, complexity, and performance.

翻译：

系统设计是定义系统的架构、组件和接口以满足特定需求的过程。关键原则包括可扩展性、可用性和可维护性。水平扩展添加更多机器来分配负载，而垂直扩展升级现有硬件。负载均衡器将传入请求分布到多个服务器。缓存通过在内存中存储频繁访问的数据来减少数据库负载。消息队列解耦组件并优雅地处理流量峰值。每个设计决策都涉及成本、复杂性和性能之间的权衡。

词汇注释：

• architecture /ˈɑːrkɪtektʃər/：架构
• component /kəmˈpoʊnənt/：组件
• scalability /ˌskeɪləˈbɪləti/：可扩展性
• availability /əˌveɪləˈbɪləti/：可用性
• maintainability /meɪnˌteɪnəˈbɪləti/：可维护性
• horizontal /ˌhɔːrəˈzɑːntl/：水平的
• vertical /ˈvɜːrtɪkl/：垂直的
• tradeoff /ˈtreɪdɔːf/：权衡