some strange storage stuff

grain-pool.go

@@ -157,6 +157,20 @@ func (p *GrainLocalPool) Purge() {
 	}
 }
 
+// RefreshExpiry resets the expiry timestamp for a living grain to now + TTL.
+// Called after successful mutations to implement a sliding inactivity window.
+func (p *GrainLocalPool) RefreshExpiry(id CartId) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	for i := range p.expiry {
+		g := p.expiry[i].Grain
+		if g != nil && g.Id == id {
+			p.expiry[i].Expires = time.Now().Add(p.Ttl)
+			break
+		}
+	}
+}
+
 // GetGrains returns a legacy view of grains (copy) for compatibility.
 func (p *GrainLocalPool) GetGrains() map[CartId]*CartGrain {
 	p.mu.RLock()
@@ -225,7 +239,12 @@ func (p *GrainLocalPool) Apply(id CartId, mutation interface{}) (*CartGrain, err
 	if err != nil || grain == nil {
 		return nil, err
 	}
-	return grain.Apply(mutation, false)
+	result, applyErr := grain.Apply(mutation, false)
+	// Sliding TTL: refresh expiry on successful non-replay mutation (Apply always non-replay here)
+	if applyErr == nil && result != nil {
+		p.RefreshExpiry(id)
+	}
+	return result, applyErr
 }
 
 // Get returns current state (legacy wrapper).