Serverless Yandex Database Internals

Resources:

• Oleg Bondar - Serverless YDB Internals
• Andrey Fomichev - YDB: multiversionality in a distributed base

Key Takeaways

Tablet is a statefull abstraction layer that is responsible for (depending on its type) having a view on a portion of the data in distributed storage, balancing the load by slicing, merging, moving tablets between the nodes, and providing the transactional guarantees in order to serve the high availability and low latency for the workloads, responsible for writing a WAL log for durability.

Key features of the tablets:

• Replication State Machine (RSM) writing the WAL log to preserve the state, restoring the state from the log, and providing guarantees like Raft or Paxos.
• ACID transaction guarantees and storing the data as the LSM-tree.
• Providing API for the layer above to interact with the tablet, e.g. insert, update, delete, etc.

The tables overview

The tablet internals

An example of the data-shard tablet

See also:

• Fauna: Lessons Learned Building a Real World, Calvin-based System (Matt Freels, Fauna)
• BigTable and Yugabyte