Snapshot archive — at1 snapshot

Instead of keeping hundreds of near-identical full copies of last night's database, AT-1 keeps one base plus a hash-chained sequence of row-level deltas. Reconstruct any night row-exact for querying — or byte-identical to the original file with --exact — and run AS OF <date> across years without a restore. A stable primary key plus a per-night schema stamp means a column added or dropped mid-chain still rebuilds, and every night is sealed so you can prove no one edited history.

Use it

# delta-chain nightly CSV snapshots into one archive (row-exact + a byte-exact recipe)
at1 snapshot build 2026-05-*.csv -o ledger.at1snap --pk id --exact

# materialize any night AS OF a date, no restore (optionally filter)
at1 snapshot asof ledger.at1snap 2026-05-14 --where status=OPEN

# reconstruct the original file byte-for-byte (sha256 matches the original)
at1 snapshot asof ledger.at1snap 2026-05-14 -o night.csv --exact

# full audit: replay every night, verify blobs + the per-night hash chain
at1 snapshot verify ledger.at1snap

# chain arbitrary nightly BINARY files (HSTs, dumps, any bytes) instead of CSV
at1 snapshot build-raw 2026-05-*.hst -o ledger.at1snap

What it gives you

  • AS-OF without restore — resolve a date to its night and materialize just that day from base + deltas, a few hundred KB of I/O rather than a full-backup restore.
  • Per-night tamper-evidence — each night chains the SHA of its delta and of the snapshot it must reconstruct to; flip one byte and the chain breaks and reconstruction refuses.
  • Schema drift, solved — rows are keyed by a stable primary key by name; a column added, dropped, or reordered across years still reconstructs.
  • build-raw — the same delta-chain over arbitrary nightly binary files (HSTs, SQL dumps, any bytes) with content-defined-chunk dedup and byte-exact AS-OF.

Honest about the numbers: the compact chain is typically 2–3× smaller than gzipping each night and grows toward ~12× over hundreds of high-overlap nights. A single solid xzover the concatenation is a touch smaller on pure bytes — but it cannot answer AS OFwithout unpacking everything, has no per-night tamper-evidence, and no O(checkpoint) day addressing. We pitch the query and the proof, never “smallest on disk.”

Part of the Regulated Archive family. See the Snapshot Archive product page and Regulated Archive.

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