Hi HN,

This is Yash, founding team at Parseable (https://github.com/parseablehq).

We've built an open source observability data lake using Rust, that handles high-cardinality data at around 100M active time series in production (https://www.parseable.com/blog/how-parseable-handles-100-mil...)

Our architecture is built around columnar design, and we use Apache Arrow for in-memory columnar processing and Apache Parquet for durable columnar storage on S3-compatible object storage. In Parseable, every labels stay as columns in the data instead of becoming a large long-lived per-series index like many TSDBs.