Actor System

Plinth uses Kameo actors for concurrent, in-memory operations that would be expensive to run on every request.

Content Caches

Location: crates/server/src/actors/core_cache.rs, crates/server/src/bricks/*/cache.rs

In-memory caches for blog posts, portfolio items, todos, tags, and site content. They avoid hitting Postgres on every page load.

Messages:

• GetAllBlogPosts — returns cached Vec<BlogListItem>
• GetBlogPost(String) — returns a full BlogPost by slug
• GetPostsByTag(String) — returns posts filtered by tag slug
• GetAllPortfolioItems — returns cached portfolio items
• GetPortfolioItemBySlug(String) — returns a single portfolio item
• GetAllTodos and GetTodosByTag(String) — return todo list items
• GetAllTags — returns all tags with post counts
• GetSiteContent(String) — returns site content by key
• InvalidateCache — clears the cache, forcing a reload from DB on next access

The cache is lazily populated: the first request after invalidation triggers a DB query, and subsequent requests are served from memory.

VectorSearch

Location: crates/server/src/actors/vector_search.rs

Handles semantic search using fastembed 384-dimensional embeddings and cosine similarity.

Messages:

• SearchSimilarArticles { query, limit } — embeds the query text and finds the most similar articles
• FindRelatedArticles { slug, limit } — finds articles related to a given post
• TrackOpinionEvolution { topic, min_similarity } — finds posts about a topic sorted chronologically (for tracking how opinions evolve over time)

The vector search path stores embeddings in Postgres via pgvector and uses the HNSW index for approximate nearest-neighbour lookup.

Lifecycle

Actors are spawned during server startup in main.rs and stored in AppState. They receive a clone of the Postgres pool for lazy data loading. Cache invalidation is triggered automatically after admin API operations (publish, delete, tag changes).