roblox-datastores

Reference for Roblox DataStoreService — saving, loading, and managing player data on the server.

Quick Reference

Basic Setup

-- Server Script (ServerScriptService)
local DataStoreService = game:GetService("DataStoreService")
local Players = game:GetService("Players")

local playerStore = DataStoreService:GetDataStore("PlayerData_v1")

local DEFAULT_DATA = {
    coins = 0,
    level = 1,
    xp = 0,
}

Loading Data (GetAsync + pcall)

Always wrap datastore calls in pcall. They can fail due to network issues or rate limits.

local function loadData(player)
    local key = "player_" .. player.UserId
    local success, data = pcall(function()
        return playerStore:GetAsync(key)
    end)

    if success then
        local result = {}
        for k, v in pairs(DEFAULT_DATA) do result[k] = v end
        if data then
            for k, v in pairs(data) do result[k] = v end
        end
        return result
    else
        warn("Failed to load data for", player.Name, ":", data)
        return nil -- signal failure; do not give default data silently
    end
end

Saving Data (SetAsync vs UpdateAsync)

Use SetAsync for simple overwrites. Use UpdateAsync when the value must be based on the current stored value (e.g., incrementing a counter safely across servers).

-- Simple save
local function saveData(player, data)
    local key = "player_" .. player.UserId
    local success, err = pcall(function()
        playerStore:SetAsync(key, data)
    end)
    if not success then
        warn("Failed to save data for", player.Name, ":", err)
    end
end

-- Atomic increment with UpdateAsync
local function addCoinsAtomic(userId, amount)
    local key = "player_" .. userId
    pcall(function()
        playerStore:UpdateAsync(key, function(current)
            current = current or { coins = 0 }
            current.coins = current.coins + amount
            return current
        end)
    end)
end

Retry Logic

local MAX_RETRIES = 3
local RETRY_DELAY = 2

local function safeGet(store, key)
    for attempt = 1, MAX_RETRIES do
        local success, result = pcall(function()
            return store:GetAsync(key)
        end)
        if success then return true, result end
        warn(string.format("GetAsync attempt %d/%d failed: %s", attempt, MAX_RETRIES, result))
        if attempt < MAX_RETRIES then task.wait(RETRY_DELAY) end
    end
    return false, nil
end

Auto-Save: PlayerRemoving + BindToClose

Server shutdown without BindToClose silently discards unsaved data.

local sessionData = {} -- [userId] = data table

Players.PlayerAdded:Connect(function(player)
    local data = loadData(player)
    if data then
        sessionData[player.UserId] = data
    else
        player:Kick("Could not load your data. Please rejoin.")
    end
end)

Players.PlayerRemoving:Connect(function(player)
    local data = sessionData[player.UserId]
    if data then
        saveData(player, data)
        sessionData[player.UserId] = nil
    end
end)

-- Flush all sessions on server shutdown
game:BindToClose(function()
    for userId, data in pairs(sessionData) do
        local key = "player_" .. userId
        pcall(function()
            playerStore:SetAsync(key, data)
        end)
    end
end)

Ordered DataStores (Leaderboards)

Values must be positive integers.

local coinsLeaderboard = DataStoreService:GetOrderedDataStore("Coins_v1")

local function setLeaderboardScore(userId, coins)
    pcall(function()
        coinsLeaderboard:SetAsync("player_" .. userId, math.floor(coins))
    end)
end

local function getTopPlayers(count)
    local success, pages = pcall(function()
        return coinsLeaderboard:GetSortedAsync(false, count) -- false = descending
    end)
    if not success then return {} end

    local results = {}
    for rank, entry in ipairs(pages:GetCurrentPage()) do
        table.insert(results, { rank = rank, userId = entry.key, score = entry.value })
    end
    return results
end

Data Versioning / Migration

Include a _version field and migrate in the load path.

local CURRENT_VERSION = 2

local function migrateData(data)
    local version = data._version or 1
    if version < 2 then
        data.coins = data.gold or 0  -- renamed field
        data.gold = nil
        data._version = 2
    end
    return data
end

Use a versioned datastore name (PlayerData_v2) for breaking schema changes.

Common Mistakes