- Index is broken down, stored, and processed as collection of shards
- Each shard is a complete Lucene Index and cannot be scaled-out
- Form Lucene performance perspective larger index is faster than series of smaller indices
- Shards are allocated to nodes and are searched independently
- At the completion of search individual shards results must be aggregated - too many shards may impact performance
- Index cannot store documents directly - types are used as buckets to index documents