Building an AI Question Paper Generator: Conquering Google Cloud Document AI, Firestore Vector Search, and Gemini

As part of the Gen AI Academy APAC , I set out to solve a major pain point for educators: manually sifting through textbooks to create grade-appropriate question papers. I built an automated Question Paper Generator using a Serverless Next.js stack, a Retrieval-Augmented Generation (RAG) architecture, and the complete Google Cloud AI suite. Teachers simply upload a textbook chapter (PDF), specify the grade and subject, and let the AI generate a fully formatted assessment quiz. While the architecture sounds straightforward, orchestrating these enterprise-grade APIs in a serverless environment presented several intense technical hurdles. Here is a deep dive into the architecture, the specific roadblocks I hit, and how I ultimately solved them. 🏗️ The RAG Architecture The application is built on Next.js 15 and deployed to Google Cloud Run . The pipeline flows as follows: Document Extraction : The PDF is uploaded and sent to Google Cloud Document AI (Document OCR Processor) to extract the raw text. Chunking & Embeddings : The text is chunked into logical paragraphs and sent to Vertex AI ( text-embedding-004 ) to generate dense vector embeddings. Vector Database : The embeddings and metadata (Grade, Subject) are stored seamlessly in Firestore using native VectorValue support. Retrieval & Generation : When a teacher requests a quiz, the query is embedded, and a findNearest Vector Search runs on Firestore. The retrieved context is passed to Google Gen AI ( gemini-3.5-flash ) to synthesize the structured question paper. 🐛 The Technical Challenges & How I Solved Them Building an end-to-end pipeline using cutting-edge SDKs often means dealing with strict schema validations and opaque error codes. Here are the major technical gotchas I faced. 1. The Document AI Region Endpoint Mismatch The Challenge: I provisioned a Document OCR processor in the asia-south1 region. However, when my Node.js client attempted to send a processing request using the processor's full resource name,