Tile38 is an in-memory geolocation data store, spatial index, and realtime geofencing server written in Go. It provides a Redis-compatible interface (RESP, HTTP, WebSocket, Telnet) for storing and querying geospatial objects (points, GeoJSON, bounding boxes, geohashes, tiles) with commands like SET, GET, NEARBY, WITHIN, INTERSECTS, and SCAN. The server supports leader/follower replication, AOF persistence, Lua scripting, and realtime geofencing via webhooks, pub/sub channels, and live connections. Its architecture is a single-binary server with a modular internal structure: a collection layer combining B-tree and R-tree indexing, a binary-encoded object and field storage for memory efficiency, a pluggable endpoint system for webhook delivery (HTTP, Kafka, MQTT, NATS, AMQP, SQS, etc.), and a custom protocol multiplexer. The codebase demonstrates high craftsmanship with reusable components like the collection data structure, glob matching, binary field lists, and endpoint manager, though some areas show signs of organic growth (e.g., large server.go, deprecated flags).