A DataStore checklist for Roblox beginners: the 8 mistakes that wipe player data

A developer published a checklist of eight common Roblox DataStoreService mistakes that cause player data loss in beginner games, including code that AI assistants generate on the first try. The guide, written for Luau in Roblox Studio, focuses on preventing overwrites of real profiles with empty defaults, covering failed loads that still save, GetAsync/SetAsync races, nil returns from UpdateAsync transforms that delete keys, and missing pcall retries.

Player data in Roblox rarely disappears because DataStoreService is "broken." It disappears because a save ran with the wrong contents, or did not run at all. The eight mistakes below are the ones I keep seeing in beginner games — and in code that an AI assistant generates on the first try. They are not about leaderboards or monetization. They are about not overwriting a real profile with empty defaults. This is written for Luau in Roblox Studio, with the current DataStore APIs: DataStoreService , UpdateAsync , pcall , retries, and BindToClose . No invented methods. No guarantee that a particular community module will stay unchanged; the patterns stand on their own. This is the classic wipe. The server calls GetAsync or UpdateAsync . The request errors — budget, outage, typo in the store name. The script catches the error and quietly continues with a default table: zero coins, empty inventory. The player moves around for a minute and leaves. You save that default table. Yesterday's progress is gone. The rule is mechanical: a session may save only if the load succeeded. If the load fails after retries, do not let the player into a state that can write. Kick them with a retry message, or keep them in a lobby that cannot trigger a save. local sessions = {} -- Player : { loaded: boolean, data: table } local function canSave player local session = sessions player return session ~= nil and session.loaded == true end Treat "loaded" as a flag you set only after a successful DataStore read, not after you filled in defaults locally. GetAsync plus SetAsync instead of UpdateAsync GetAsync returns a copy. SetAsync writes whatever you hand it. If two servers both load the same player — a trade, a teleport, a rare double session — the slower SetAsync wins and the other server's writes vanish. UpdateAsync applies a transform on the latest stored value and retries the transform if the value changed underneath you. Officially, that transform may run more than once and must not yield . local DataStoreService = game:GetService "DataStoreService" local store = DataStoreService:GetDataStore "PlayerData v1" local function keyFor player return "player " .. player.UserId end Use UpdateAsync for the load so you can also set a session token and for the save. Keep SetAsync for values that are safe to overwrite blindly, which a full player profile is not. nil from the This one feels like a typo and behaves like a delete. If the transform function returns nil , Roblox removes the key . A missed return data , a typo, or an early return in an error branch will erase the profile. The call can still succeed. You will not get an error that says "deleted." -- Dangerous: a forgotten return deletes the key. store:UpdateAsync key, function old local data = old or { coins = 0 } data.coins += 5 -- missing: return data end -- Correct: always return a table, never nil, unless you intend to delete. store:UpdateAsync key, function old local data = old or { coins = 0 } data.coins += 5 return data end Never "clear" a missing field by returning nothing. If old is nil , that only means the key is new — return a fresh default. Do not return nil to mean "leave it unchanged"; if you must abort a write, the documented way is to throw inside the transform so the update is cancelled. pcall , no retries Every DataStore call can throw. Without pcall , one failed request can abort the rest of PlayerRemoving and skip the save entirely. With pcall but no retry, a single budget blip has the same outcome. local MAX ATTEMPTS = 5 local function updateWithRetry key, transform for attempt = 1, MAX ATTEMPTS do local ok, result = pcall function return store:UpdateAsync key, transform end if ok then return true, result end warn "UpdateAsync failed %s , attempt %d" :format tostring result , attempt task.wait 2 ^ attempt - 1 end return false, nil end Use task.wait , not wait . The backoff is exponential and stays well under the 30-second BindToClose window if you cap the attempts. If the final leave-save still fails, log it and do not pretend it succeeded. BindToClose — or a fight with PlayerRemoving When a server shuts down, players are removed and the instance is killed. PlayerRemoving may not get enough time, especially in Studio or during an update. BindToClose gives you up to 30 seconds after the close starts. You should save remaining sessions there. The second half of the bug is running two unsynchronized saves at once. Use a per-player saving flag, and only save if canSave player is true. local Players = game:GetService "Players" local RunService = game:GetService "RunService" local function save player local session = sessions player if not canSave player or session.saving then return end session.saving = true local ok = updateWithRetry keyFor player , function old -- Write the in-memory session, which only exists because load succeeded. return session.data end session.saving = false if not ok then warn "Final save failed for", player.UserId end end Players.PlayerRemoving:Connect function player save player sessions player = nil end game:BindToClose function local leftover = {} for , player in ipairs Players:GetPlayers do table.insert leftover, player end for , player in ipairs leftover do task.spawn function save player end end -- In Studio a short wait is usually enough; live servers should wait -- until the spawned saves finish or the 30-second limit is close. if RunService:IsStudio then task.wait 2 else task.wait 8 end end A production version should wait on a counter or a BindableEvent instead of a fixed task.wait 8 . The point of the snippet is the structure, not a magic number. player.Name Names change. UserIds do not. A key like "player " .. player.Name looks readable and will silently start a new, empty profile after a rename — or, worse, eventually collide with a name another account used to have. Always use player.UserId . Keep a version suffix on the store name PlayerData v1 when you change the shape of the table, not in a way that depends on the display name. DataStores have a request budget you can inspect it with DataStoreService:GetRequestBudgetForRequestType . Autosaving every few seconds for every player will spend that budget on writes you do not need. Then the leave-save, the one that actually matters, gets 429 or a budget error and fails. A practical rhythm is: save on leave, save in BindToClose , and autosave on a slow interval minutes, not seconds , only for sessions that have actually changed. Check the budget before a non-urgent save and skip a cycle rather than blasting retries during an already tight shutdown. If the character can collect coins before session.loaded is true, you will either drop those coins or, if you then save defaults mixed with new rewards, risk writing a half-initialized table. Gate the loop: the player does not receive currency, inventory, or teleports until the session exists. The related wipe is trusting the client to send the table you store. A RemoteEvent that says "here is my data, please save it" lets an exploiter send an empty inventory — or a full one. The server should already have the session in memory. The client may request an action "buy this", "equip that" ; the server validates, mutates session.data , and saves that. local function load player local ok, data = updateWithRetry keyFor player , function old local profile = old or { coins = 0, joins = 0, } profile.joins += 1 return profile -- never nil end if not ok or type data ~= "table" then player:Kick "Deine Daten konnten nicht geladen werden. Bitte erneut beitreten." return end sessions player = { loaded = true, data = data, saving = false } end Players.PlayerAdded:Connect function player load player end Using UpdateAsync on load also increments joins atomically. If you later add a session lock, put it in this same transform — and release it in the save on leave — instead of inventing a second store. These DataStore rules belong in a patterns file that lives outside the chat, next to a short status note for the game you are actually building. That is the working method packed into my German-language kit, Roblox Second Brain . 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