InfluxDB 3 Core (IOx) is a production-grade, open-source time-series database written in Rust. It ingests data via line protocol (HTTP/gRPC), stores it in Apache Parquet on object storage (S3, Azure, GCP, local), and serves queries via SQL (DataFusion), InfluxQL, and FlightSQL. The architecture is a single binary (`influxdb3`) that combines an HTTP server (port 8181), gRPC FlightSQL endpoint, CLI, and an embedded Python processing engine for plugin-based triggers. The system is designed for low-latency last-value queries, high-throughput writes, and efficient columnar storage with catalog persistence as versioned binary logs and snapshots on object store. The codebase is a large Rust workspace (~40+ crates) with a clear separation of concerns: core libraries (`core/`) for query planning, Arrow utilities, authorization, and metrics; server crates (`influxdb3_*`) for catalog management, write buffering, processing engine, and system tables. Key entry points include `influxdb3/src/main.rs` (CLI), `influxdb3_server/src/unified_service/` (HTTP/gRPC routing), and `influxdb3_catalog/src/` (catalog operations). The query engine is built on a forked DataFusion with custom physical optimizers (gapfill, dedup, sort, union) and InfluxQL planning. External dependencies include object store backends, protobuf for gRPC, and Python (via PyO3) for plugins. The repository demonstrates high craftsmanship with several reusable patterns: a versioned binary record format for catalog persistence with forward-compatibility guarantees, a hook-based cache system with S3-FIFO eviction, a generic copy-on-write repository pattern, and a run-optimized merge sort for streaming sorted data. However, the large workspace, forked DataFusion pinned to a commit, and multiple catalog versions (v1–v4) introduce maintenance drift risks. The codebase is actively maintained with extensive tests, benchmarks, and CI/CD.