Trillian
A transparent, highly scalable and cryptographically verifiable data
...The system is designed for horizontal scale with gRPC APIs, enabling multiple frontends and sequencers to operate over a shared backend. Common use cases include certificate transparency, package registries, and audit logs where public verifiability or tamper evidence is required. Trillian exposes both “log” and “map” primitives so developers can choose between append-only timelines or verifiable dictionaries depending on their data model. By making verification independent of trust in the operator, trillian helps build systems that are auditable by external parties.