Foreword by Michael Wildpaner

At their core, both Site Reliability Engineering and Security Engineering are concerned with keeping a system usable. Issues like broken releases, capacity shortages, and misconfigurations can make a system unusable (at least temporarily). Security or privacy incidents that break the trust of users also undermine the usefulness of a system. Consequently, system security is top of mind for SREs.

On the design level, security has become a highly dynamic property of distributed systems. We’ve come a long way from passwordless accounts on early Unix-based telephony switches (nobody had a modem to dial into them, or so people thought), static username/password combinations, and static firewall rules. These days, we instead use time-limited access tokens and high-dimensional risk assessment at millions of requests per second. Granular cryptography of data in flight and at rest, combined with frequent key rotation, makes key management an additional dependency of any networking, processing, or storage system that deals with sensitive information. Building and operating these infrastructure security software systems requires close collaboration between the original system designers, security engineers, and SREs.

The security of distributed systems has an additional, more personal, meaning for me. From my university days until I joined Google, I had a side career in offensive security with a focus on network penetration testing. I learned a lot about the fragility ...