| Interface | Description | 
|---|---|
| Clock | Mockable interface for tracking time. | 
| RateLimiter | A rate limiter interface used by Samza components to limit throughput of operations
 against a resource. | 
| Class | Description | 
|---|---|
| BlockingEnvelopeMap | 
 BlockingEnvelopeMap is a helper class for SystemConsumer implementations. | 
| NoOpMetricsRegistry | MetricsRegistryimplementation for when no actual metrics need to be
 recorded but a registry is still required. | 
| SinglePartitionWithoutOffsetsSystemAdmin | A simple helper admin class that defines a single partition (partition 0) for
 a given system. | 
| TimestampedValue<V> | An immutable pair of a value, and its corresponding timestamp. |