Throughout the years PHP has added support for several extensions, libraries, and algorithms to encrypt and decrypt data. With several libraries and extensions with various levels of maintenance, several algorithms each potentially carrying pros and cons, some even inherently
高可用架构设计最核心的就是两点：解耦和冗余。解耦包括业务状态分离（无状态架构设计）、分库分表等。冗余包括缓存、CDN、主从备份、主主备份、GeoDNS 等。一个好的架构设计需要在产品迭代的不同阶段选择合适的技术，从而既能在合理的成本条件下有效保障当前的业务需求，又能考虑到业务下一步发展的可能性。原文链接：[How to design a system to scale to your first 100 million users](https://levelup.gitconnected.com/how-to-design-a-system-to-scale-to-your-first-100-million-users-4450a2f9703d)
QUICK SUMMARY ↬ What are absolute units? What are the differences between relative and absolute units, and how do we create accurate sizes on the web? In this article, Elad Shechter explains why CSS absolute units aren’t so absolute.