Prometheus has gained significant popularity as a mature CNCF project, with widespread adoption by over 500,000 companies and a substantial presence on GitHub. To ensure compatibility, especially with long-term storage and third-party services, Prometheus co-creator Julius Volz initiated compatibility testing against PromQL and Prometheus itself, which expanded to include OpenMetrics. This led to the development of the Prometheus Conformance program in collaboration with Richard Hartmann, aiming to standardize compatibility testing for Prometheus, PromQL, and Remote Write. The initiative ensures vendors maintain compliance with evolving Prometheus standards, as demonstrated by Logz.io's implementation, which shows 100% PromQL compatibility, supporting the reuse of existing dashboards and scripts. This effort underscores the commitment to maintaining observability at scale, supported by open-source collaboration, while guarding against false compatibility claims by vendors.