/roblox-datastores

name: roblox-datastores
description: >
  Persist player data in Roblox with DataStoreService: GetDataStore, GetAsync/
  SetAsync/UpdateAsync/IncrementAsync wrapped in pcall, load-on-join and
  save-on-leave plus BindToClose, retries, and OrderedDataStore leaderboards. Use
  when saving or loading persistent data in a Roblox experience — when the user
  mentions DataStore, DataStoreService, GetAsync, SetAsync, UpdateAsync, save player
  data, or leaderboards. For general Luau scripting use roblox-luau.

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 `Script`s, never `LocalScript`s. 2. **Get a store, then read/write by key.** `DataStoreService:GetDataStore("Name")`; key per player is usually `"Player_" .. player.UserId`. 3. **Wrap every call in `pcall`.** `GetAsync`/`SetAsync`/`UpdateAsync` are network calls that can fail; an unguarded failure errors the thread and risks data loss. 4. **Load on `PlayerAdded`, save on `PlayerRemoving`, and also `BindToClose`.** A leaving player and a shutting-down server both need a final save. 5. **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. 6. **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 clo