geohashim

Data and storage

Storage, replication and data contracts, checked under faults.

Seven repos about keeping data correct: a graph database written from scratch, Raft and a CRDT attacked by fault simulators and fuzzers, a crash-consistency tester for storage code, PostgreSQL migrations tried on a copy under live traffic, contracts for JSON event streams, and lossless time-series compression.

See the seven repos On the landing route
Repos
7
Passing tests
888, one dot each, run in October 2026 the way each repo's CI runs them
Languages
TypeScript, Go, Rust

    The seven repos

    Open a repo for its project page: what it does stage by stage, with real runs.

    • atlas-graph-db

      686 passing tests

      Featured Storage engine, transactions and its own query language

      A graph database written from scratch in TypeScript, with a write-ahead log, crash recovery, atomic transactions and a Cypher-like query language (AQL).

      Language
      TypeScript
      Stack
      Node.js, Fastify, Angular
      Counted with
      pnpm test (468 engine and server tests plus 218 web app tests)

      GitHub: atlas-graph-db

    • crdt-notes

      39 passing tests

      Local-first notes on a fuzzed CRDT

      A local-first notes app on a from-scratch TypeScript CRDT, with a fuzzer that attacks convergence over a hostile network and six deliberate bugs it must catch.

      Language
      TypeScript
      Stack
      Angular, WebSocket relay, Vitest, Playwright
      Counted with
      npm test and npm run e2e (37 unit tests plus 2 end-to-end tests in two browsers)

      GitHub: crdt-notes

    • quorum-lab

      38 passing tests

      Raft under a deterministic fault simulator

      Raft written from scratch in Go, attacked by a deterministic simulator that partitions, crashes and skews clocks, checks safety after every event, and must catch six deliberate bugs.

      Language
      Go
      Stack
      Go standard library only, deterministic simulation, linearizability checking
      Counted with
      go test -count=1 -json ./... (32 tests plus 6 subtests)

      GitHub: quorum-lab

    • wal-crash

      35 passing tests

      Every state a power cut can leave on disk

      Records a program's file-system calls with strace, builds every state a power failure could leave on disk, and runs the program's own recovery on each to find which lost operation broke a promise.

      Language
      Go
      Stack
      Go standard library only, strace, SQLite in a Docker dev image
      Counted with
      go test -race -count=1 -json ./... (33 tests plus 2 subtests)

      GitHub: wal-crash

    • migrate-safe

      40 passing tests

      What a PostgreSQL migration will lock

      Shows what a PostgreSQL migration will do to a live database before it ships, by running it on a copy under live traffic, and checks its linter's predictions against the server in CI.

      Language
      Go
      Stack
      Go and PostgreSQL (pgx), Docker
      Counted with
      go test -race -count=1 -json ./... (28 tests plus 12 subtests, against a live PostgreSQL as in CI)

      GitHub: migrate-safe

    • schema-drift

      29 passing tests

      Breaking-change checks for JSON events

      A contract checker for JSON event streams that decides whether a schema change breaks readers or writers, and proves each breaking verdict with a concrete event.

      Language
      Go
      Stack
      Go standard library only, GitHub Actions
      Counted with
      go test ./...

      GitHub: schema-drift

    • tsz

      21 passing tests

      Time-series compression, best codec per block

      Lossless compression for (i64, f64) time series in Rust that measures Gorilla, Chimp, Chimp128 and a decimal codec on every block and writes the smallest, so values printed as text shrink up to 29 times.

      Language
      Rust
      Stack
      Rust standard library only, no dependencies, GitHub Actions
      Counted with
      cargo test --locked (4 unit, 5 cli, 4 corrupt, 7 roundtrip, 1 doc test; the 1M-series soak test is ignored by default)

      GitHub: tsz