An SRE (Site Reliability Engineer) is an engineer responsible for the reliability of systems in production, who treats operations as a software problem: availability, performance, capacity, incident management and automation of repetitive tasks.
The practice was born at Google in the early 2000s and popularized by the book Site Reliability Engineering (2016). It spread a vocabulary that has become common:
- SLI and SLO: the measured reliability indicator and the target to reach;
- error budget: the tolerated margin of unavailability, which arbitrates between new features and stabilization;
- toil: repetitive manual work, to be reduced;
- blameless post-mortems after each incident.
SRE shares a lot with DevOps, but with a more precise goal: reliability that is quantified, measured and negotiated with product. At Google, the team must spend at least half its time on engineering work rather than pure operations.
Why it matters when hiring
A first SRE is hired when production becomes critical to revenue and incidents get expensive. Many jobs titled "SRE" are really ops or DevOps roles. The strong signal on a resume: SLOs defined and tracked, on-call duty, post-mortems written, and code written to eliminate manual work. Ask the candidate to walk you through their worst incident, from detection to fix.