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ZippyDB (Meta key-value store)

Definition

ZippyDB is Meta's distributed key-value store, used as the backing store for the unified BLOB-storage metadata schema in the re-architected AI storage stack.

Role in AI Storage

In the 2026 BLOB-storage re-architecture, ZippyDB replaced the multi-layer metadata system (namelayer, volumeslayer, containerlayer) with a single flat schema enabling O(1) lookup per chunk to resolve object paths to (blockId, offset, size) tuples — a step-function improvement over the prior cascading metadata lookups that could add hundreds of milliseconds and cross regions.

(Source: sources/2026-07-01-meta-ai-storage-blueprint-at-scale)

Scale and workload

ZippyDB is Meta's most widely used key-value store, backing product metadata, counters, and configuration, and can serve billions of operations per second across a globally distributed fleet. Its database hosts are referred to as the ZServer fleet. (Source: sources/2026-09-03-meta-zgateway-learnings-from-putting-a-proxy-in-front-of-zippydb)

Proxy layer: ZGateway

As of 2026, Meta is unifying ZippyDB client traffic through ZGateway, a stateless proxy tier between ZippyDB clients and the ZServer fleet. In the original direct-access model every client connected to every database host it needed, producing a dense many-to-many mesh of TLS connections — a typical client held tens of thousands of outbound connections and a typical database host accepted tens of thousands of inbound ones. That mesh made database-host fan-in scale with the client population (every new cohort degraded every host) and turned reconnection storms into file-descriptor-exhaustion reboot loops. ZGateway collapses the mesh into two bounded hops and adds cross-client batching/coalescing, per-tenant admission control (DLS), read caching, control-plane load balancing, and cross-region failover. ZGateway runs Meta's thick C++ ZippyDB client as its engine — "a ZippyDB client run as a managed service." See collapse-many-to-many-mesh-into-two-bounded-hops. (Source: sources/2026-09-03-meta-zgateway-learnings-from-putting-a-proxy-in-front-of-zippydb)

Prior References

Meta's 2021 blog post "ZippyDB: The Architecture of a Distributed Key-Value Store" provides the original public architecture description (not ingested on this wiki).

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