idxsub

Idxsub is a term used in software design to describe an index-based subscription mechanism. It refers to a pattern where clients subscribe to a stream of events or updates that are filtered by a specific index or key. This allows selective notification and efficient data delivery in systems that handle large or partitioned datasets.

Core concepts include the index or key that serves as the filter, a subscription handle to manage lifecycle, and an event stream that delivers updates relevant to the chosen index. Subscriptions can be durable or non-durable, depending on the system, and may provide either live updates or access to replayed past events.

Typical use cases include database change streams, real-time dashboards, event-driven architectures, sensor networks, and message brokers that support keyed subscriptions. By associating each subscriber with a narrow index, idxsub reduces noise and bandwidth, since each consumer only receives events tied to its interest.

Implementation considerations involve selecting an underlying mechanism such as pub/sub, message queues, or reactive streams. Key requirements often include per-index ordering guarantees, idempotent event processing, and backpressure handling. API surface commonly offers subscribe(index, callback), unsubscribe(handle), and sometimes retrievePastEvents(index, since) for initialization.

Limitations to watch for include increased system complexity as the number of indices grows, potential scalability challenges with high-cardinality workloads, and the need for careful fault tolerance and backoff strategies to handle dropped or duplicate events.

See also keyed subscription, pub/sub, reactive streams, and change data capture.