The main objective of site reliability engineering (SRE) is to ensure a reliable and scalable operation of software systems while maintaining high availability. SRE combines principles of software engineering and systems administration to automate operational tasks and improve system performance. SREs monitor services, manage incidents, and conduct postmortems to prevent future failures. They work closely with development teams to implement practices like continuous integration and continuous delivery (CI/CD) to enhance code quality. By establishing service-level objectives, SREs aim to balance reliability with agility in deployments.