Cross-Platform Search Engine App

My goal is to launch a lean mobile application on both iOS and Android that acts as a dedicated text-based search engine in a single language (English only, no multilingual switching needed). The core of the job is the full stack build: database or crawler setup for indexing, an efficient search algorithm, and a clean Flutter / React Native (or other cross-platform) front-end that returns fast, relevant results from typed queries.

Key deliverables
• Native-level performance app for iOS & Android
• Backend service that indexes content I supply and exposes a JSON/REST endpoint for text queries
• Simple, modern UI with one search bar, results list, and basic settings screen
• Complete, well-commented source code plus run/compile instructions

Acceptance criteria
1. Typed queries return results under 300 ms for a 10 k document set on mid-range devices.
2. Search relevance verified by a provided test suite of 50 sample queries.
3. App passes App Store and Google Play upload checks with no critical warnings.

I will supply the initial dataset and can spin up a server if your preferred solution needs one; otherwise I’m happy to see a fully on-device option. Please outline the stack you prefer, any third-party libraries you’d integrate, and a rough milestone plan when you reply.