Vitess

The MySQL sharding system planetscale maintains, and the piece that makes 768 servers answer to one hostname. Paged now that this wiki has read its documentation rather than only heard it named (vitess-query-serving-docs, v23.0).

The parts this wiki has evidence for

VTGate — the proxy applications actually connect to. It “routes traffic to the correct VTTablet servers and returns consolidated results back to the client,” speaks the MySQL wire protocol so “your applications can connect to VTGate as if it is a MySQL Server,” and picks destinations by weighing the sharding scheme, latency requirements and instance availability. It is also where cross-shard merging happens.

VTTablet — the per-MySQL-instance agent that VTGate routes work to, and the layer where Vitess parses queries a second time.

VSchema and vindexes — the sharding metadata. A vindex maps a column value to a shard, and a query’s plan depends on the VSchema as much as on the SQL. A routing operator that can’t name a vindex scatters.

Keyspaces — sharded or unsharded; an unsharded keyspace maps to a single MySQL database. Shards are assigned by key ranges over binary values, with 0x80 as the midpoint, which allows uneven splits.

VEXPLAIN — the plan/trace tool, from Vitess 16. Five modes; TRACE reports ShardsQueried per operator and KEYS proposes sharding-key candidates from a statement’s shape.

Where it sits

The proxy-router half of this spoke’s embedded↔distributed axis: turso collapses the database into the process, Vitess explodes it across a fleet and spends its effort making the fleet look like one server. Its design commitment — push work down to MySQL, merge only what can’t be pushed — is why it can keep the MySQL interface honest without becoming a distributed query engine.

Sibling: Neki, planetscale‘s Postgres equivalent, which this wiki has only as a name.

Version caveat: everything above is v23.0 documentation read on 2026-08-03; operator names, VEXPLAIN modes and defaults move between releases.

Related

database-sharding · cross-shard-queries · vitess-query-serving-docs · planetscale · planetscale-768-servers · turso · synthesis