fix(rust): evict in-memory cache entries at the expiry boundary

Matches Python evict_cache, which uses expiration <= now

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

litellm-rust/crates/cache-memory/src/cache.rs

@@ -154,7 +154,7 @@ impl<V: Clone> InMemoryCache<V> {
         while let Some(Reverse((expiration, key))) = state.expiration_heap.peek().cloned() {
             if state.expirations.get(&key).copied() != Some(expiration) {
                 state.expiration_heap.pop();
-            } else if expiration < now {
+            } else if expiration <= now {
                 state.expiration_heap.pop();
                 Self::remove(state, &key);
             } else {

litellm-rust/crates/cache-memory/tests/cache.rs

@@ -45,6 +45,24 @@ fn default_explicit_and_override_ttls_follow_python_rules(clock: Arc<AtomicU64>)
     );
 }
 
+#[rstest]
+fn write_at_expiry_boundary_refreshes_ttl(clock: Arc<AtomicU64>) {
+    let cache = cache(clock.clone(), 4);
+    cache
+        .set_cache("key", "first".into(), Some(Duration::from_secs(10)))
+        .unwrap();
+    clock.store(110, Ordering::SeqCst);
+    cache
+        .set_cache("key", "second".into(), Some(Duration::from_secs(10)))
+        .unwrap();
+    assert_eq!(
+        cache.expires_at("key").unwrap(),
+        Some(Duration::from_secs(120))
+    );
+    clock.store(115, Ordering::SeqCst);
+    assert_eq!(cache.get_cache("key").unwrap(), Some("second".into()));
+}
+
 #[rstest]
 fn capacity_evicts_earliest_and_ignores_stale_heap_entries(clock: Arc<AtomicU64>) {
     let cache = cache(clock, 2);