A code freeze means no code can be altered or modified during the frozen time, and developers will not make any additional changes. Developers can only modify the code in the event of critical flaws and to the extent required to correct those vital problems. Primarily developers observe a code freeze during the final phase of software development when the software product has reached the delivery state.

Reliability engineering focuses on the ability of systems to perform as it is intended to and function without failure in a specified environment, for the required time duration. Reliability engineering can be applied across the entire lifecycle of software development. It is designed to increase the dependability of a product by detecting potential reliability issues early in the software development cycle, and correcting causes of failure that do occur.

Software reliability can be defined as the probability of a failure-free operation of a computer system over a specified period, under a set of specific conditions. It is an important factor in determining software quality. Site reliability engineering (SRE) is a software approach to IT operations that helps organizations to improve the reliability of their systems.

Since Google coined the term, the role of an SRE has evolved as the industry has shifted toward large-scale distributed microservices. An SRE’s job is to determine how to make systems more reliable and resilient.