roblox-datalisted

# Roblox data Read [`../../references/roblox-engineering.md`](../../references/roblox-engineering.md). Inspect the existing data layer and every writer before choosing a storage pattern. ## Classify the state - Durable player or game state belongs in DataStoreService. - Frequent, ephemeral cross-server coordination belongs in MemoryStoreService with explicit expiration and recovery when an entry disappears. - One-way cross-server notifications may use MessagingService, but the message should identify authoritative state that receivers can reread. Do not make delivery itself the durable record. - Local caches need an owner, invalidation rule, maximum lifetime, and fallback when the backing service fails. ## Preserve correctness - Keep service access server-side. Define the key format, serializable schema, schema version, defaults, validation, migration, and ownership of each mutation. - Use atomic update patterns for concurrent or retry-sensitive writes. Keep update callbacks pure and non-yielding; derive the new value only from their arguments and immutable inputs. - Make rewards, purchases, and other consequential mutations idempotent. Record the operation identifier with the durable outcome so a retry cannot grant twice. - Use a session lease when multiple servers could write the same player record. Define acquisition, renewal, release, stale-owner recovery, and what gameplay can continue after ownership is lost. - Wrap service calls, distinguish retryable failure from