Platform limits

The limits on this page belong to Roblox, not to Twill, and Roblox changes them. This page describes the shape of each limit and links to the page that carries the current number. Read that page before designing right up against one.

Most budgets scale with the player count. Nearly every request budget is a base plus a per-player term, so a system that runs perfectly in an empty test place can be over budget on a full server, and inside it again the moment players leave. Test at population, not alone.

DataStore

What matters most is the shape of the data, not its size.

• JSON only. No Vector3, CFrame, or Color3. Use Serialize.
• No NaN, no infinity.
• Text must be valid UTF-8.
• Named and numbered keys cannot mix. { 1, 2, Name = "x" } becomes [1,2]. The string key is lost with no error.
• Numbering cannot have gaps. { [1] = "a", [3] = "b" } comes back with string keys.

Serialize.FindUnstorable catches all of these, and a key that is neither a string nor a number besides. Data.Edit runs it for you and answers "unsupported".

Beyond the shape, three ceilings are worth knowing about:

Ceiling	Why it matters
Value size per key	Generous, but a profile that grows without bound will reach it. Reach for Compress before redesigning.
Requests per minute	Scales with concurrent players, is counted for the whole experience rather than per server, and is shared with Open Cloud. Store asks the engine for the remaining budget before each call, and queues its own writes per key.
Throughput per key	A separate budget from the request count, measured in bytes per minute. A large profile saved often can exhaust this while staying well inside the request budget.

That last one is the trap, because it is invisible until a profile grows. Two saves of a large profile can cost more than a hundred saves of a small one.

Names for stores, scopes, and keys are short. Building a key out of several joined values is the usual way to overrun that.

Versioning. Every write keeps previous versions for a retention window, which is what makes an accidental Data.Reset recoverable. It is a window, not an archive.

Current numbers: Data store error codes and limits.

MessagingService

Delivery is best effort, not guaranteed. Roblox states this plainly, and it is the constraint to design around. A message that never arrives must not leave your game in a broken state.

This is why cross-server player writes go through Data.Edit instead. It routes through Store, which lands the change in the player’s saved data whether or not any server was listening, and never writes over a session it does not own.

• The message size ceiling is around a kilobyte, far smaller than a DataStore value. This is the limit Compress.Encode exists to help with, and it is easy to exceed with an ordinary table.
• Sends, receives, and subscriptions all have their own budgets, each scaling with players or servers. Shared counts this server’s publishes and subscriptions against them, and waits a moment for room rather than failing at once.

Use it for announcements, shutdown coordination, and cache invalidation. Do not use it as a data channel.

Current numbers: MessagingService.

MemoryStore

Fast, shared across servers, and temporary. Three structures are offered: a sorted map, a queue, and a hash map.

• Everything expires. There is a default lifetime and you can set your own. Nothing here is storage; treat it as a cache with a deadline.
• Memory and requests are both quotas, both scaling with the number of players, and both counted for the whole experience rather than per server.
• Requests are counted in units, not calls. Some calls cost more than one: reading a range costs per item returned, and an update costs more than a read. A loop that looks like one call per tick can be several.
• Values must be JSON-serialisable, so the same shape notes as DataStore apply.

Shared counts this server’s requests and retries a throttled one. Because the quota belongs to the whole experience, it counts a fair share rather than an exact figure.

Current numbers: Memory stores.

Ordered data stores

Leaderboards run on ordered data stores, which hold whole numbers only and have a tighter write budget per server than ordinary data stores. Board reads the top on a timer, gathers changes into one write per entry, and writes only as fast as the budget reported by the engine allows.

Teleports

• At most 50 players per call. Teleport splits a larger group into calls of 50, and reserves one server first so the group stays together.
• Teleport data passes through the client. Anything sent in it can be read, and possibly altered. Teleport keeps the data in a memory store and sends only a signed ticket.
• Studio cannot teleport. Test teleports in a published place.

Current details: Teleport between places.

Experience configs

Configs are read on the server only. A value has a size ceiling per type, and an experience has a ceiling on the number of active configs. Config answers every declared key from a default until configs arrive, and keeps the default when a delivered value has the wrong type.

Current details: Experience configs.

Attributes

Attributes hold a fixed set of value types: strings, numbers, booleans, and a handful of Roblox datatypes such as Vector3, CFrame, Color3, and UDim2.

They cannot hold a table, and they cannot hold an Instance. Names are restricted to alphanumeric characters with a few separators, and RBX is reserved.

Authorization uses an attribute for a player’s rank precisely because attributes replicate on their own and cannot be written by a client. For anything with structure, use Replication instead.

Current details: Instance attributes.

The player list

It sorts IntValue and NumberValue only. Text is displayed but never sorted.

The direct consequence: a BigNumber reads correctly and ranks nowhere, because no value object can hold it as a number. See Count past the number limit for the way around it.

Web quota

Several APIs spend the server’s HTTP budget: GetUserIdFromNameAsync, GetRolesInGroupAsync, text filtering, and Marketplace calls.

Twill guards the two paths that are easiest to abuse:

• The admin console screens rank and rate before parsing a command line, because Cmdr’s own argument validation resolves usernames through Roblox.
• Authorization remembers group answers per player and drops them through Scope.Player.

Filter adds no limit of its own, so the platform’s per-user limit is the one you meet. Filter when text is submitted, not every time it is drawn.

The general rule

Design away from a ceiling, not right up against it. Finding a limit in production always costs more than leaving headroom did, and the budgets that scale with players are found exactly when a game is doing well.