(I used to work at SingleStore, and now work at Antithesis)

SingleStore (f.k.a. MemSQL) used lock-free skiplists extensively as the backing storage of their rowstore tables and indexes. Adam Prout (ex CTO) wrote about it here: https://www.singlestore.com/blog/what-is-skiplist-why-skipli...

When SingleStore added a Columnar storage option (LSM tree), L0 was simply a rowstore table. Since rowstore was already a highly optimized, durable, and large-scale storage engine, it allowed L0 to absorb a highly concurrent transactional write workload. This capability was a key part of SingleStore's ability to handle HTAP workloads. If you want to learn more, take a look at this paper which documents the entire system end-to-end: https://dl.acm.org/doi/10.1145/3514221.3526055