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Scalability

“Scalability” 是架构非功能需求之一,涉及吞吐、延迟、成本曲线。常区分 scale up(垂直)与 scale out(水平);良好 scalability 意味着增加资源带来近似线性的容量提升。

  1. “Load tests measured scalability up to five times normal traffic.” (压测衡量了高达正常流量五倍时的可扩展性。)
  2. “Sharding improved database scalability for large tenants.” (分片提升了大租户场景下的数据库可扩展性。)
  3. “Scalability planning should include cost per additional user.” (可扩展性规划应包含每新增用户的成本。)

scalable + -ity,scale 表规模,-ity 表抽象性质。

“scalable” + “-ity”:可扩展这一特性。

CAP 定理、Amdahl 定律与 scalability 讨论紧密相关;过早优化 scalability 不如先验证产品市场契合。

  • 固定搭配: “horizontal scalability” (水平可扩展性), “scalability bottleneck” (扩展瓶颈), “scalability test” (扩展性测试)
  • 形容词: scalable

scalable 的名词形式——ability to scale,即 scalability。

“Poor scalability showed up as rising p99 latency long before the servers maxed out CPU.” (可扩展性不足表现为 p99 延迟上升,远早于 CPU 打满。)