roblox-datastores

Roblox DataStores

Persist data across sessions in Roblox with DataStoreService: loading on join, saving on leave and shutdown, safe updates, retries, and ordered stores for leaderboards. Server-side only.

When to use

• Use to save/load player progress (coins, inventory, levels), build persistent

leaderboards, or fix data loss, overwrites, and throttling.

• Use when server code calls DataStoreService, GetDataStore, GetAsync,

SetAsync, UpdateAsync, or GetOrderedDataStore.

When not to use:* general scripting, services, remotes, the client/server split → roblox-luau. High-frequency temporary state (matchmaking, per-round) → memory stores (a different service). Engine-agnostic persistence theory → save-systems.

Core workflow

1. Enable Studio access once. File → Game Settings → Security → *Enable Studio

Access to API Services* (use a test place; Studio hits live data). DataStores work only from server Scripts, never LocalScripts.

1. Get a store, then read/write by key. DataStoreService:GetDataStore("Name");

key per player is usually "Player_" .. player.UserId.

1. Wrap every call in `pcall`. GetAsync/SetAsync/UpdateAsync are network

calls that can fail; an unguarded failure errors the thread and risks data loss.

1. Load on `PlayerAdded`, save on `PlayerRemoving`, and also `BindToClose`. A

leaving player and a shutting-down server both need a final save.

1. Prefer `UpdateAsync` for read-modify-write (multi-server safe) over SetAsync

(blind overwrite). On a failed load, do not overwrite with defaults — abort the save so you don't wipe good data.

1. Use `OrderedDataStore` for ranked data (leaderboards) via GetSortedAsync.

Test by joining, changing data, rejoining, and confirming it persisted.

Patterns

1. Load on join (pcall-guarded)

local DataStoreService = game:GetService("DataStoreService")
local Players = game:GetService("Players")
local store = DataStoreService:GetDataStore("PlayerData")

local DEFAULT = { Coins = 0, Level = 1 }

Players.PlayerAdded:Connect(function(player)
    local key = "Player_" .. player.UserId
    local ok, data = pcall(function()
        return store:GetAsync(key)
    end)

    if not ok then
        -- Load FAILED (network). Do not treat as a new player; flag so we never save
        -- over their real data with defaults.
        warn("Load failed for", player.Name, data)
        player:SetAttribute("DataLoaded", false)
        return
    end

    player:SetAttribute("DataLoaded", true)
    local profile = data or DEFAULT          -- nil == genuinely new player
    applyToLeaderstats(player, profile)
end)

2. Save with UpdateAsync (multi-server safe)

-- UpdateAsync reads the latest value, then writes what the callback returns.
-- The callback MUST NOT yield (no task.wait, no further Async calls inside it).
local function savePlayer(player)
    if player:GetAttribute("DataLoaded") == false then return end  -- never overwrite on a bad load
    local key = "Player_" .. player.UserId
    local newData = gatherDataFor(player)    -- a plain table of serializable values

    local ok, err = pcall(function()
        store:UpdateAsync(key, function(old)
            -- merge/decide here; return nil to cancel the write
            return newData
        end)
    end)
    if not ok then warn("Save failed for", player.Name, err) end
end

3. Save on leave AND on shutdown

Players.PlayerRemoving:Connect(savePlayer)

-- BindToClose runs when the server shuts down; save everyone still in.
-- It has a limited time budget, so save in parallel and yield until done.
game:BindToClose(function()
    local players = Players:GetPlayers()
    local remaining = #players
    if remaining == 0 then return end
    for _, player in players do
        task.spawn(function()
            savePlayer(player)
            remaining -= 1
        end)
    end
    while remaining > 0 do task.wait() end
end)

4. Retry with backoff (transient failures)

local function withRetry(fn, attempts)
    attempts = attempts or 3
    for i = 1, attempts do
        local ok, result = pcall(fn)
        if ok then return true, result end
        if i < attempts then task.wait(2 ^ i) end   -- 2s, 4s, ... backoff
    end
    return false
end

local ok, data = withRetry(function() return store:GetAsync(key) end)

5. Increment a counter

-- IncrementAsync is a convenience for integer read-modify-write (still wrap it).
local ok, newTotal = pcall(function()
    return store:IncrementAsync("Visits_" .. player.UserId, 1)
end)

6. Leaderboard with OrderedDataStore

local boards = DataStoreService:GetOrderedDataStore("Coins")

-- Write a player's score (call when it changes, not every frame).
pcall(function() boards:SetAsync("Player_" .. player.UserId, coins) end)

-- Read the top 10, descending.
local ok, pages = pcall(function()
    return boards:GetSortedAsync(false, 10)   -- ascending=false → highest first
end)
if ok then
    for rank, entry in ipairs(pages:GetCurrentPage()) do
        print(rank, entry.key, entry.value)   -- entry.value is the number
    end
end

Pitfalls

• Unhandled failure wipes progress → always pcall Async calls; on a failed

load, mark the session and refuse to save so defaults never overwrite real data.

• `SetAsync` race between servers → two servers writing the same key can clobber

each other. Use UpdateAsync for read-modify-write so each write sees the latest.

• Yielding inside the `UpdateAsync` callback → the callback can't call

task.wait or other Async functions; compute the new value beforehand and return it.

• No `BindToClose` save → players in the server at shutdown lose unsaved progress;

add game:BindToClose and wait for saves to finish within its budget.

• Throttling / "too many requests" → respect per-key and per-minute limits; don't

save on every value change. Batch and save on a timer / on leave. GetAsync is cached briefly, so immediate re-reads may be stale.

• Storing non-serializable values → only JSON-serializable data persists: numbers,

strings, booleans, and tables with string/number keys. Instances, Vector3, CFrame, and functions do not — serialize them to plain tables first.

• Testing without API access → DataStores silently can't be used in Studio until

Enable Studio Access to API Services is on (and they don't work from a LocalScript).

• `DataStoreKeyInfo` is nil for ordered stores → OrderedDataStore doesn't

support versioning/metadata; use a regular DataStore when you need those.

References

• For session locking (preventing duplicate data across servers), versioning/

metadata with DataStoreSetOptions, ordered-store pagination (AdvanceToNextPageAsync), the key error codes and request limits, and Right-to-be-Forgotten compliance, read references/sessions-and-limits.md.

Related skills

• roblox-luau — services, instances, events, and the server/client model.
• save-systems — engine-agnostic serialization, slots, and migration.