Update README

core/mvcc/README.md

@@ -10,6 +10,12 @@ Run tests:
 cargo test
 ```
 
+Test coverage report:
+
+```console
+cargo tarpaulin -o html
+```
+
 Run benchmarks:
 
 ```console

core/mvcc/database/src/clock.rs

@@ -0,0 +1,26 @@
+use std::sync::atomic::{AtomicU64, Ordering};
+
+/// Logical clock.
+pub trait LogicalClock {
+    fn get_timestamp(&self) -> u64;
+}
+
+/// A node-local clock backed by an atomic counter.
+#[derive(Debug, Default)]
+pub struct LocalClock {
+    ts_sequence: AtomicU64,
+}
+
+impl LocalClock {
+    pub fn new() -> Self {
+        Self {
+            ts_sequence: AtomicU64::new(0),
+        }
+    }
+}
+
+impl LogicalClock for LocalClock {
+    fn get_timestamp(&self) -> u64 {
+        self.ts_sequence.fetch_add(1, Ordering::SeqCst)
+    }
+}