movies-diary/docs/adr/0003-local-follow-direct-db.md

Local follows bypass ActivityPub, share storage

ADR-0002 introduced SocialIdentity so the domain never branches on local vs remote, but the adapter (CompositeSocialAdapter) still routed everything through k_ap — meaning a local user following another local user triggered WebFinger resolution, HTTP signature verification, and inbox delivery to the same instance. Wasteful on any hardware, unacceptable on an N100.

Decision

Commands branch in the adapter, queries don't.

• SocialCommand methods in CompositeSocialAdapter check the SocialIdentity variant. Local targets get direct SQL writes to the ap_followers/ap_following tables (via a domain FollowRepository port). Remote targets delegate to k_ap::ActivityPubService as before.
• SocialQuery methods go through the domain port only — a single SQL query that left-joins ap_followers/ap_following against both users (local) and ap_remote_actors (remote), returning SocialActor directly.
• Local follows store the full actor URL (https://instance.example/users/{uuid}) in remote_actor_url, same format as remote follows. k_ap's AP collection endpoints read from these tables unchanged, so local relationships are visible to the fediverse automatically.
• Local user metadata (display name, avatar) is resolved from the users table at query time — no duplication into ap_remote_actors.
• Follow acceptance is required for both local and remote — no behavioral divergence.
• Local follow events (FollowRequested, FollowAccepted) are not broadcast as AP activities. The fediverse discovers local relationships passively via collection endpoints.

Considered Options

• Keep routing local through k_ap — rejected because it wastes CPU/network on self-delivery and creates an unnecessary runtime dependency on federation for local social features.
• Separate local_follows table — rejected because it creates two sources of truth for the same concept and requires merging in collection endpoints.
• Insert local users into ap_remote_actors — rejected because it duplicates profile data and requires sync when local users update their profile.