Site Reliability Engineers (SREs) sits at the intersection of software engineering and systems engineering. While there are potentially infinite permutations and combinations of how infrastructure and software components can be put together to achieve an objective, focusing on foundational skills allows SREs to work with complex systems and software, regardless of whether these systems are proprietary, 3rd party, open systems, run on cloud/on-prem infrastructure, etc. Particularly important is to gain a deep understanding of how these areas of systems and infrastructure relate to each other and interact with each other. The combination of software and systems engineering skills is rare and is generally built over time with exposure to a wide variety of infrastructure, systems, and software. SREs bring in engineering practices to keep the site up. Each distributed system is an agglomeration of many components. SREs validate business requirements, convert them to SLAs for each of the components that constitute the distributed system, monitor and measure adherence to SLAs, re-architect or scale out to mitigate or avoid SLA breaches, add these learnings as feedback to new systems or projects and thereby reduce operational toil. Hence SREs play a vital role right from the day 0 design of the system.