Building a Multi-Engine 3D Generation API: Routing, Credits, and Webhooks

How I designed the API layer for Trify3D — a platform that routes one input across multiple AI 3D engines (Tripo3D, Meshy, Rodin) so users can compare meshes side by side. This post covers provider routing, async job management with Trigger.dev, idempotency for credit safety, and webhook delivery. The Problem Every AI 3D engine has a blind spot. Tripo3D is fast (~48 seconds) and great at hard-surface props, but it flattens organic detail. Meshy handles characters and creatures more cleanly (~76 seconds), but its topology gets messy on hard surfaces. Rodin produces the highest-fidelity PBR textures (~90 seconds), but it's the slowest and most expensive. If a user picks one engine, they're stuck with its weaknesses. To compare results, they'd need three separate accounts, three subscriptions, and three credit pools — then manually juggle browser tabs. I built Trify3D to solve this: one input, every engine, one credit pool. A user uploads an image or writes a prompt, the platform routes it to multiple 3D AI engines simultaneously, and they compare the meshes side by side before exporting the winner. This post is about the API layer that makes that work. Architecture Overview Here's the high-level flow: Client Request │ ▼ ┌──────────────────┐ │ API Gateway │ Bearer auth, rate limit, idempotency check │ (trify3d.com) │ └────────┬─────────┘ │ ▼ ┌──────────────────┐ │ Provider Router │ Routes to Tripo3D / Meshy / Rodin │ (mode + model) │ based on mode + model prefix └────────┬─────────┘ │ ┌────┼────┐ ▼ ▼ ▼ ┌──────┐┌──────┐┌──────┐ │Tripo3D││Meshy ││Rodin │ Async generation └──┬───┘└──┬───┘└──┬───┘ │ │ │ └───────┼───────┘ ▼ ┌──────────────────┐ │ Trigger.dev │ Job orchestration, retries, 10-min timeout │ (async runner) │ └────────┬─────────┘ │ ┌────┴────┐ ▼ ▼ ┌────────┐ ┌──────────┐ │ Poll │ │ Webhook │ Client picks one or both │ (GET) │ │ (POST) │ └────────┘ └──────────┘ Three decisions drove this architecture: Async-first — 3D generation takes 48–90 seconds. No HTTP reque