Hybrid Logical Clocks
Hybrid Logical Clocks (HLC) are a timestamping mechanism that combines physical and logical clocks to provide causally consistent ordering of events in distributed systems. They address the limitations of purely physical clocks (like NTP inaccuracies) and purely logical clocks (like Lamport clocks lacking real-time information) by maintaining both a physical time component and a logical counter. This allows HLC to offer both causality preservation and bounded deviation from physical time, making it useful for applications requiring both ordering and approximate real-time timestamps.
Developers should learn and use Hybrid Logical Clocks when building distributed systems that need to order events causally while also maintaining some connection to real-world time, such as in databases, logging systems, or event-sourcing architectures. It is particularly valuable in scenarios where clock synchronization is imperfect (e.g., across data centers or cloud regions), as it ensures logical consistency without relying solely on accurate physical clocks. Use cases include distributed databases like CockroachDB for transaction ordering, or in microservices for tracking event sequences in audit logs.