Developed a secure machine-to-machine authentication flow for the Twins microservices platform, focusing on robust service-to-service communication. Leveraging Java and OAuth2/OIDC standards, the work replaced a generic login with a client credentials flow, ensuring only authorized services can interact internally. Token introspection was enhanced to reliably identify M2M clients by supporting a fallback from the 'sub' to 'client_id' claim in JWTs, addressing edge cases in client identification. All changes were delivered in the alcosi/twins repository, establishing a strong security baseline for internal APIs and preparing the system for scalable onboarding of additional services through improved authentication and backend integration.