SYSTEM Cited by 2 sources
FoundationDB¶
FoundationDB (FDB) is an open-source, strictly serializable, ordered key-value store with multi-key ACID transactions, originally built by the FoundationDB company, acquired by Apple in 2015, and open-sourced in 2018.
It shows up in the sysdesign-wiki as the metadata repository under Datadog's systems/husky — its transaction guarantee is the primitive Husky relies on to atomically swap "N old fragments" for "1 new fragment" in a compaction, so queries always see a consistent table state before-or-after a compaction (never partially applied). (Source: sources/2025-01-29-datadog-husky-efficient-compaction-at-datadog-scale)
Why teams pick it for metadata¶
- Multi-key ACID across the whole keyspace — rare among scalable KV stores; most either scope transactions to a partition or drop strict serialisability.
- Ordered keyspace — range scans are first-class, so metadata layouts that need "all fragments in this (table, time-window) bucket" work naturally.
- Designed for metadata / control-plane workloads — the transactional guarantees cost throughput relative to a partitioned KV store, so it's canonical for control/metadata layers sitting in front of much larger object-storage data planes (the Husky shape).
Seen in¶
- sources/2025-01-29-datadog-husky-efficient-compaction-at-datadog-scale — backs Husky's fragment-metadata repository; transactional fragment-swap is the atomicity primitive behind compaction consistency.
- sources/2024-02-15-flyio-globally-distributed-object-storage-with-tigris — Tigris's metadata plane: "redundant FoundationDB clusters in our regions to track objects." Second production metadata-store instance in the wiki, shape- parallel to the Husky one — FDB as the ACID metadata layer in front of a much larger, eventually-consistent byte/object plane (object-storage byte cache + QuiCK-style distribution queue here; fragment files in object storage at Datadog). Reinforces FDB's canonical role as the metadata substrate for distributed-systems-scale storage control planes. See patterns/metadata-db-plus-object-cache-tier for the generalised architectural pattern.