Player data for Roblox that loses nothing, fails loudly, and never stutters a frame.
KeepBlox keeps session-locked player profiles on DataStore. It reads and writes the same records as
ProfileStore and speaks its lock protocol, so a game can switch by changing one require, run old and
new servers side by side during the rollout, and switch back.
Status: 0.9.6. Everything below is proven in the simulator, against ProfileStore, five other libraries and a game with no library. It is also checked on Roblox's real DataStore, MessagingService and MemoryStore in a private test experience (
tests/live), overload included. It runs in one live public game (Grabby Pit) since early October 2026. That is one game and a short time: try it in a test place first.
Each promise is a spec, and the simulation checks the data invariants after every write, across many virtual servers and random fault schedules:
- An acknowledged save is never lost, and only one server can write a profile at a time.
- A hand-over request never ends the wrong session, a load that gives up never leaves its server holding the key, and a live server whose MemoryStore hangs is never taken for dead.
- A crash loses about one 4 s heartbeat of play: each beat carries a snapshot the next server takes.
- A failed load never writes; data that is not a profile is quarantined, never overwritten.
- A server that loses the session freezes its copy at once, so trades and purchases stop on stale data.
- One bad value (NaN, bad UTF-8, a cycle) never costs the play around it: it is repaired in what is stored and reported with its path. What cannot be repaired (over 4 MB, a mixed table, an array with holes, number keys: shapes Roblox would silently cut or rename) is refused, and the last good snapshot is stored instead.
- Offline messages are consumed exactly once; purchases are granted once and never lost.
- Shutdown releases every profile within the deadline; no call retries forever, and a load answers within
loadTimeoutin all. - Under overload the budget goes to saves first: a load waits for the server's budget instead of polling it, so the saves that hand players over are not throttled.
- Saving is spread across frames and respects the DataStore request budget: a 1 MB profile's save costs at most about 4.2 ms in any one frame.
- A release can be rolled back without locking out a player who played on it (
writeVersion).
The checker is checked too: 31 small slips in the code that keeps these promises each make the suite
fail (tests/Mutate.luau), and the save check is fuzzed against the store's encoding.
- Offline and admin edits that never kick a player (
store:edit), and offline messages (store:message). - Trades between two profiles that land in both or in neither (
store:trade). - Shared documents for guilds and clans, updated atomically from any server (
KeepBlox.shared). - Jobs due at a time, kept in a data store and run by whichever server sweeps first, with no
MemoryStore quota to outgrow (
KeepBlox.schedule). - Counts every server adds to, summed across the game in batches over sharded keys, each batch
counted once (
KeepBlox.tally). - Leaderboards mirrored to ordered data stores (
leaderboards). - A schema with numbered, testable migrations; deep defaults for template stores.
- Releases you can roll back: migrations with a way back (
{ up, down }) andwriteVersion, so the release before reads everything, renames included. Lapis and DocumentService'sbackwardsCompatiblecovers only changes old code can read as they are. - Purchases through
KeepBlox.processReceipt, and version history with a safe restore that names the purchases it takes back. Optional compression for large profiles, and Studio modes that never touch live data. - Types for Luau (
--!strictthroughout) and roblox-ts (types/index.d.ts).
Every library runs unmodified in the same simulator: the same fakes of DataStore, MemoryStore, MessagingService and the engine, the same players, faults and seeds (worst case over 20 seeds).
| Library | Violations | A crash loses (steps of play) | Slowest open (s) | Failed opens | Requests per player-hour |
|---|---|---|---|---|---|
| KeepBlox | 0 | 4 | 9.4 | 0 | 13.1 + 13.1 |
| ProfileStore | 0 | 287 | 46.6 | 20 | 13.6 + 13.6 |
| ProfileService | 0 | 29 | 65.8 | 27 | 122 + 122 |
| DocumentService | 0 | 0 (player locked out: 20 of 40 rejoins) | 15.9 | 389 | 25.9 + 25.9 |
| Lapis | 0 | 0 (player locked out: 20 of 40 rejoins) | 11.9 | 374 | 14 + 14 |
| DataStore2 | 61 | 287 | 8.8 | 0 | 0 + 1 |
| Suphi's DataStore Module | 1 | 0 (player locked out: 20 of 40 rejoins) | 0.5 | 355 | 1 + 120 |
| No library (GetAsync / SetAsync, as the Roblox guides teach) | 63 | 51 | 0.2 | 0 | 1 + 60.7 |
Requests are data store reads + writes. KeepBlox also spends 45 MemoryStore units per player-hour on its
server heartbeat, which is how a dead server is known within seconds and how a crash loses only one
beat of play. The full tables, every scenario and the methodology are in
bench/Benchmarks.md; luneblox run bench/Report 20 makes them.
KeepBlox is built to take over from the libraries games already use.
From ProfileStore or ProfileService, change one line; the keys and their format stay as they are:
local ProfileStore = require(path.to.KeepBlox.Compat.ProfileStore)From DocumentService, Lapis, DataKeep, DataStore2 or Suphi's DataStore Module, point a store at the old data: each key moves on its first load, and the old data is only read.
local store = KeepBlox.store("Profiles", {
template = { coins = 0 },
import = KeepBlox.importers.DocumentService({ store = "PlayerData" }),
})- Wally:
KeepBlox = "xopoiii/keepblox@0.9.6"under[server-dependencies]. - pesde:
pesde add xopoiii/keepblox -t roblox_server -a KeepBlox. - Studio:
KeepBlox.rbxmfrom the latest release.
More in Installation.
rokit install # the pinned toolchain
lefthook install # the gates, before every commit
sh scripts/run-tests.sh
luneblox run tests/Mutate --yes # mutation adequacy: every slip must fail the suite (about 16 min)
luneblox run bench/download && luneblox run bench/Report 20 # the benchmarks
luneblox run tests/live/Serve # the live check, only in the test experience (tests/live/README.md)
npm ci --prefix docs && npm run build --prefix docs # the documentation siteTests run on LuneBlox, which runs the Luau version and fast flags Roblox runs.
MIT. See LICENSE. Vendored reference code in tests/reference/ keeps its own license.