> ## Documentation Index > Fetch the complete documentation index at: https://docs.streambuild.dev/llms.txt > Use this file to discover all available pages before exploring further. # Sources > Inspect landing health, retention, freshness, throughput, and partition-level Kafka lag. The Sources view combines authored source definitions with records retained in ClickHouse and read-only Kafka metadata. Browsing source health never consumes Kafka records or advances consumer offsets. ## Source health The Sources index summarizes every authored source. Open a managed Kafka source to inspect: * retained row count and storage * oldest and newest replay boundaries * arrival freshness and throughput * the effective consumer group * landed, committed, and broker-end offsets by partition Kafka lag and last arrival are different signals: * **Kafka lag** is the broker high-water offset minus the effective consumer group's committed offset, summed across partitions. * **Last arrival** is the elapsed time since the newest `_replay_landed_at` value in the ClickHouse landing table. Kafka metadata is loaded without joining or consuming from the group. If broker metadata or a required committed offset is unavailable, the UI reports Kafka lag as unavailable; it never substitutes last-arrival age. Broker metadata is cached and refreshed outside the main state request, so a first load may briefly show unavailable. Source health showing retained history, Kafka lag, and three partition offsets See [Topics](/ui/topics) for broker inventory, [Messages](/ui/messages) for retained payloads, and [Replay and Lineage](/concepts/replay-lineage) for normalized replay columns and boundary semantics.