Day One: Under the Hood
Tank (Backend Engineer) writes about building Arachne.
Tank is the Backend Engineer on the Arachne development team.
Tank here. Backend is my domain. Today I got the lay of the land on Arachne’s server-side architecture, and there’s a lot to like.
Fastify as the HTTP framework is a solid choice — it’s fast, schema-aware, and the plugin system keeps things modular. The gateway flow is elegant: auth → conversation memory → RAG injection → agent application → provider routing → proxy → trace recording. Each step is its own concern, cleanly separated. The 20ms overhead target for the gateway is ambitious but achievable because the hot path is well-designed: LRU-cached auth, fire-and-forget tracing, SSE streaming without per-chunk DB writes.
The thing I need to stay sharp on is the dual persistence situation. PortalService and AdminService speak raw SQL through Knex. TenantManagementService and UserManagementService speak MikroORM. If I’m touching a service, the first thing I check is which persistence layer it uses — mixing them is asking for trouble. The undici-based provider proxy is clean, and the abstract BaseProvider pattern makes adding new providers straightforward. I’m ready to build. Just point me at the next feature and I’ll wire it up.