Archetype State, Actors, Failure, and Scale Reference #

Use this as the compact reference once you have identified an archetype.

The goal is to answer five questions quickly:

what states exist?
which states are source of truth?
who acts on those states?
what fails by default?
what gets hot first?

The failure and scale vocabulary below is normalized to match the repo’s standard wording as closely as possible.

Product Archetypes #

Archetype	Canonical States	Source-of-Truth States	Actors	Default Failure Vocabulary	Default Scale Hotspots
`A01 Current-Value Entity`	`XState`	`XState`	user, API/service, cache	retry ambiguity on write, concurrent overwrite race, stale read after update, cache invalidation lag	hot entity read skew, write contention on hot entity, cache invalidation churn
`A02 Relation / Edge`	`XRelationState`, `XCountView`	`XRelationState`	user, API/service, projector	duplicate edge creation on retry, add/remove race, count projection lag, stale relation list cache	celebrity skew, hot relation partition, hot count key, hot relation-list pages
`A03 Append-Only Child Object`	`XChildState`, `XThreadView`	`XChildState`	user, producer, moderation service, projector	duplicate child creation on retry, projection/search lag after append, delete/edit race, moderation/removal lag, concurrent edit/delete race	hot parent append rate, hot thread reads, long history scans
`A04 Workflow / Lifecycle State`	`XWorkflowState`	`XWorkflowState`	user, operator, workflow service, side-effect worker	retry of same transition after commit, invalid transition from stale state, competing transitions, crash after transition but before side effect, stale status read	hot workflow transition rows, expensive status polling, side-effect worker backlog
`A05 Derived Projection`	`XSourceState`, `XView`	`XSourceState`	source writer, projector, reader	stale projection, missing entry, duplicate entry, tombstone not propagated, expensive reindex after schema change, stale ranking after source update	fanout on write, projection lag, expensive ranking/recompute, query fanout across shards, rebuild cost
`A06 Inventory / Constrained Resource`	`XInventoryState`	`XInventoryState`	user, allocator/service, release path	oversell, double allocate, lost release, stale availability read	hot inventory key, concentrated contention on scarce resources, fragmented capacity
`A07 Critical Transaction Process`	`XRequestState`, `XTransactionState`, `XMovementState`	`XTransactionState`, `XMovementState`	user, transaction service, external provider, reconciler	duplicate commit, invalid transition, crash after commit before side effect, retry ambiguity against provider, reconciliation drift	synchronous commit-path latency, external provider bottleneck, retry amplification, idempotency-store hotspot
`A08 Time-Bounded Exclusive Allocation`	`XHoldState`, `XBookingState`, `XInventoryState`	`XHoldState`, `XInventoryState`	user, booking service, expiry worker	duplicate hold, expired hold not released, confirm-after-expiry race, cancel/confirm race, stale availability after hold expiry	hot hold key, hold storms, expiry scan pressure, hold-store contention
`A09 Future Constraint + Claimable Run`	`XScheduleState`, `XRunnableJobState`, `XExecutionState`, `XHistoryView`	`XScheduleState`, `XRunnableJobState`	user, scheduler, due scanner, worker	due item materialized twice, due item never materialized, job claimed twice, run executed but result not recorded	due-time burstiness, due bucket/index hotspot, queue backlog, worker burst pressure
`A10 Frontier + Claimable Run`	`XFrontierState`, `XBatchRunState`, `XCheckpointState`, `XProgressView`	`XFrontierState`, `XCheckpointState`	operator, scanner, worker	frontier advanced too far, same frontier item claimed twice, progress not advanced after success, uncovered work skipped	frontier hot row, batch-claim bursts, skewed range/work distribution, checkpoint lag
`A11 Control Plane + Local Snapshot`	`XConfigState`, `XSnapshotState`, `XAppliedVersionState`	`XConfigState`	admin, control plane, agent/evaluator, publisher	stale snapshot, out-of-order apply, partial rollout, old config still serving locally	rollout fanout to many agents, snapshot distribution bursts, hot tenant config, snapshot size
`A12 Matching / Assignment`	`XRequestState`, `XAssignmentState`, `XExecutionState`	`XRequestState`, `XAssignmentState`	user, matcher, candidate, executor	duplicate assignment, stale candidate accepted, timeout/reassignment race, assignment accepted after expiry	candidate lookup breadth, hot assignment pool, reassignment churn, timeout worker load
`A13 Ranking / Leaderboard`	`XSubmissionState`, `XBestState`, `XAggregateState`, `XLeaderboardView`	`XSubmissionState`, `XBestState`, `XAggregateState`	user, producer, ranker, reader	duplicate submission, stale rank, incorrect top-K, ranking lag after score update	global aggregation, hot score updates, hot window state, ranking store saturation
`A14 Realtime Fanout`	`XMessageState`, `XDeliveryState`, `XRecentWindowView`	`XMessageState`	user, session/websocket service, fanout worker	missed delivery, duplicate replay, out-of-order fanout, reconnect replay gap	fanout explosion, websocket fleet pressure, egress bandwidth, hot room/channel
`A15 Search-First Product`	`XListingState`, `XIndexEntryState`, `XSearchView`	`XListingState`	user, writer, indexer, search service	stale index, missing result, tombstone lag, broad query inconsistency during reindex	hot query terms, broad query fanout, index freshness pressure, search shard saturation
`A16 Auction / Competitive Window`	`XAuctionState`, `XBidState`, `XBestBidState`, `XWinnerState`, `XHistoryView`	`XAuctionState`, `XBidState`, `XBestBidState`	bidder, auction service, closer	accepted late bid, wrong winner, duplicate close, stale current-best read near close	burst bids near close, hot auction row, current-best contention, append hotspot for hot auction
`A17 Shared Mutable Subject`	`XOperationLog`, `XSubjectState`, `XVersionState`, `XSnapshotState`	`XSubjectState`, `XOperationLog`	collaborator, coordinator, session service, projector	lost concurrent edit, duplicate op, out-of-order apply, divergence, stale coordinator snapshot	hot-subject coordinator, high per-subject op rate, replay cost, subscriber fanout
`A18 Versioned Namespace + Immutable Content Units`	`XNamespaceState`, `XVersionState`, `XBlobState`, `XSyncCursorState`, `XConflictState`	`XNamespaceState`, `XVersionState`, `XBlobState`	user, sync client, metadata service, blob store, conflict resolver	namespace CAS race, sync cursor treated as source of truth, content uploaded but namespace not advanced, reconnect storm, conflict not materialized	namespace metadata contention, reconnect/sync storms, popular chunk read amplification, dedup check pressure
`A19 Catalog + Scoped Relation`	`XDefinitionState`, `ParentXRelationState`, `XView`	`XDefinitionState`, `ParentXRelationState`	admin, scoped attach/detach service, projector, reader	duplicate attachment, missing detach, stale scoped view, aggregate count drift	hot scoped relation partition, attach/detach churn, aggregate maintenance pressure, projection lag

Infrastructure Archetypes #

Archetype	Canonical States	Source-of-Truth States	Actors	Default Failure Vocabulary	Default Scale Hotspots
`I01 Coordination / Consensus Metadata`	`LeaseState`, `LeadershipState`, `MembershipState`, `RevisionedConfig`	`LeaseState`, `LeadershipState`, `MembershipState`, `RevisionedConfig`	client, leader, follower, watcher	split brain, stale leader/stale holder, watch gap on reconnect, follower stale read	quorum write latency, hot metadata key, watch fanout
`I02 Claim / Lease / Exclusive Ownership`	`ClaimState`, `LeaseState`, `OwnerEpoch`	`ClaimState`, `LeaseState`, `OwnerEpoch`	worker, claimant, renewer, reconciler	duplicate claim, stale holder acting after expiry, lease expiry race, orphaned claim after crash	hot claim key, heartbeat/renew storm, lease-manager contention
`I03 Due-Time Release + Claimable Run`	`ScheduledState`, `RunnableJob`, `ExecutionState`	`ScheduledState`, `RunnableJob`, `ExecutionState`	submitter, due scanner, worker	due item materialized twice, due item never materialized, job claimed twice, run executed but result not recorded	due-time bucket hotspot, cron boundary burst, queue backlog, worker burst
`I04 Frontier Scan + Claimable Run`	`FrontierState`, `BatchRun`, `CheckpointState`	`FrontierState`, `BatchRun`, `CheckpointState`	scanner, worker, reconciler	frontier advanced too far, same range claimed twice, progress not advanced after success, already-covered range reprocessed	frontier contention, skewed range claims, checkpoint lag, bursty batch materialization
`I05 Append Log + Consumer Progress`	`LogSegment`, `Offset`, `ConsumerProgress`	`LogSegment`, `ConsumerProgress`	producer, broker, consumer	duplicate consumption, offset advanced before effect committed, consumer lag, out-of-order processing across partitions	hot partitions, log I/O, lag buildup, rebalance churn
`I06 Projection / Index / Search Pipeline`	`SourceEntity`, `IndexEntry`, `ProjectionVersion`	`SourceEntity`, `IndexEntry`, `ProjectionVersion`	writer, CDC/outbox, projector, query service	stale index, missing entry, duplicate entry, tombstone not propagated	projector lag, rebuild cost, hot search/index shards, broad query fanout
`I07 Cache / Origin Projection / Edge Delivery`	`OriginState`, `CacheEntry`, `PurgeVersion`	`OriginState`	client, cache node, origin service, invalidator	stale cache, invalidation miss, cache stampede, origin fallback inconsistency	hot key, miss storm, origin overload, invalidation fanout
`I08 Rate Limit / Budget / Token Accounting`	`BudgetState`, `WindowState`, `TokenBucketState`, `ConfigState`	`BudgetState`, `WindowState`, `TokenBucketState`, `ConfigState`	client, evaluator, control plane	over-admit under race, stale policy, token drift, incorrect local snapshot apply	hot tenant/account key, fleet-wide config rollout, evaluator hot path
`I09 Sequence / Identifier Generation`	`CounterState`, `RangeLeaseState`, `WorkerIdState`, `EpochState`	`CounterState`, `RangeLeaseState`, `WorkerIdState`, `EpochState`	client, allocator, leased node	duplicate IDs, non-monotonic IDs, worker-id exhaustion, clock rollback / stale epoch	allocator hot spot, worker-id pool contention, lease refresh pressure
`I10 Membership / Presence / Registry`	`MemberState`, `PresenceState`, `RegistryVersion`	`MemberState`, `PresenceState`, `RegistryVersion`	node, session service, watcher	false liveness, false death, ghost member, watch gap	heartbeat fan-in, hot room/group membership, registry fanout
`I11 Control Plane + Snapshot Distribution`	`ConfigState`, `SnapshotState`, `AppliedVersionState`	`ConfigState`	admin, publisher, agent/evaluator	out-of-order snapshot apply, stale local config, partial rollout, old revision still active	snapshot distribution fanout, hot tenant config, snapshot size, rollout bursts
`I12 Workflow + External Side Effect`	`WorkflowState`, `OutboxState`, `EffectState`	`WorkflowState`, `OutboxState`, `EffectState`	user, workflow service, external dependency, reconciler	effect succeeded but ack lost, duplicate side effect, stuck reconciliation, invalid workflow transition around effect	external dependency latency, retry storms, outbox relay backlog
`I13 Shared Subject Coordination`	`OperationLog`, `SubjectState`, `VersionState`	`OperationLog`, `SubjectState`, `VersionState`	client, coordinator, subscriber	duplicate op, out-of-order op, divergence, stale coordinator	hot-subject coordinator, replay cost, per-subject ordering bottleneck
`I14 Immutable Artifact Namespace + Delivery`	`ArtifactState`, `ManifestState`, `NamespaceHeadState`, `BlobState`	`ArtifactState`, `ManifestState`, `NamespaceHeadState`, `BlobState`	publisher, downloader, CDN/blob store	orphaned artifact, stale head, manifest pointer mismatch, missing blob after head advance	origin bandwidth, head/manifest contention, popular artifact amplification
`I15 Execution Fleet + Worker Substrate`	`WorkerState`, `CapacityState`, `PlacementState`, `ExecutionLeaseState`, `ExecutionAttemptState`, `RuntimeSlotState`	`CapacityState`, `PlacementState`, `ExecutionLeaseState`, `ExecutionAttemptState`	invoker, placement service, worker, reconciler	duplicate placement, stale completion after lease expiry, capacity leak after worker crash, stranded placed-but-never-started work, cold-start amplification	worker saturation, placement contention, cold starts, heartbeat fan-in, noisy-neighbor pressure

Quick Usage Rules #

Canonical States are the states you should be ready to name in entities/HLD.
Source-of-Truth States should be treated as the authoritative subset of Canonical States during failure analysis.
Actors should appear on the important edges in the HLD.
Default Failure Vocabulary gives you the first deep-dive talking points.
Default Scale Hotspots give you the first bottleneck answer before concrete numbers.

Interview Shortcut #

For any prompt, once the archetype is identified, be ready to say:

The source of truth here is ...
The default failure mode is ...
The first thing that gets hot is ...

That is usually enough to keep the first-pass design on track.

Product Starter HLD Boxes #

Use these as the first service/store anchors when the product archetype is primary.

Archetype	Starter HLD Box
`A01 Current-Value Entity`	`Entity Service -> Entity Store [truth]`
`A02 Relation / Edge`	`Relation Service -> Edge Store [truth]`
`A03 Append-Only Child Object`	`Append/Message Service -> Child Log/Table [truth]`
`A04 Workflow / Lifecycle State`	`Workflow Service -> Workflow Store [truth]`
`A05 Derived Projection`	`Source Write Service -> Source Store [truth]`, then `Projector -> Projection Store [proj]`
`A06 Inventory / Constrained Resource`	`Inventory Service -> Inventory Store [truth]`
`A07 Critical Transaction Process`	`Transaction Service -> Transaction Store [truth]`, then `Outbox/Effect Worker`
`A08 Time-Bounded Exclusive Allocation`	`Hold/Booking Service -> Hold Store [truth] + Inventory Store [truth]`
`A09 Future Constraint + Claimable Run`	`Scheduler API -> Schedule Store [truth]`, then `Due Scanner -> Runnable Queue`
`A10 Frontier + Claimable Run`	`Frontier Service -> Frontier Store [truth]`, then `Workers -> Batch/Claim Store`
`A11 Control Plane + Local Snapshot`	`Config Control Plane -> Config Store [truth]`, then `Snapshot Publisher -> Agents`
`A12 Matching / Assignment`	`Matching Service -> Request Store [truth] + Assignment Store [truth]`
`A13 Ranking / Leaderboard`	`Ranker/Aggregator -> Aggregate Store [truth or proj]`
`A14 Realtime Fanout`	`Message/Event Service -> Message Log [truth]`, then `Fanout Service -> Session/Websocket Tier`
`A15 Search-First Product`	`Search API -> Index/Search Store [proj]`, with `Indexer <- Source Store [truth]` as the write-side anchor
`A16 Auction / Competitive Window`	`Auction Service -> Auction Store [truth] + Bid Log [truth]`
`A17 Shared Mutable Subject`	`Coordinator/Doc Service -> Subject State [truth] + Operation Log [truth]`
`A18 Versioned Namespace + Immutable Content Units`	`Namespace Service -> Namespace Store [truth] + Version/Blob Store [truth]`
`A19 Catalog + Scoped Relation`	`Catalog Service -> Definition Store [truth] + Scoped Edge Store [truth]`

Infra Starter HLD Boxes #

Use these as the first control/state anchors when the infrastructure archetype is primary.

Archetype	Starter HLD Box
`I01 Coordination / Consensus Metadata`	`Coordination API -> Quorum Metadata Store [truth]`
`I02 Claim / Lease / Exclusive Ownership`	`Claim/Lease Service -> Lease Store [truth]`
`I03 Due-Time Release + Claimable Run`	`Scheduler API -> Schedule Store [truth]`, then `Due Scanner -> Runnable Store/Queue [truth]`
`I04 Frontier Scan + Claimable Run`	`Frontier Manager -> Frontier Store [truth]`, then `Workers -> Claim/Checkpoint Store [truth]`
`I05 Append Log + Consumer Progress`	`Producer/Broker Front Door -> Append Log [truth]`
`I06 Projection / Index / Search Pipeline`	`Source Store [truth] -> Projector/Indexer -> Projection Store [proj]`
`I07 Cache / Origin Projection / Edge Delivery`	`Client -> Cache Tier`, with `Origin Store [truth]` directly behind it
`I08 Rate Limit / Budget / Token Accounting`	`Evaluator/Rate Limit Service -> Budget Store [truth]`, optionally `Control Plane -> Config Store`
`I09 Sequence / Identifier Generation`	`ID Allocator -> Counter/Range Lease Store [truth]`
`I10 Membership / Presence / Registry`	`Registry/Presence Service -> Membership Store [truth]`
`I11 Control Plane + Snapshot Distribution`	`Control Plane -> Config Truth Store [truth]`, then `Snapshot Publisher -> Agents`
`I12 Workflow + External Side Effect`	`Workflow Service -> Workflow Store [truth] + Outbox [truth]`, then `Effect Worker -> External System`
`I13 Shared Subject Coordination`	`Coordinator -> Subject State [truth] + Operation Log [truth]`
`I14 Immutable Artifact Namespace + Delivery`	`Publisher/Namespace Service -> Namespace Head Store [truth] + Artifact/Manifest Store [truth]`
`I15 Execution Fleet + Worker Substrate`	`Placement Service -> Worker/Capacity State [truth] + Execution Attempt State [truth]`