Flowrite - Europe's First LLM Email Assistant

Flowrite was a pioneering AI startup — one of the first companies in Europe to build a production-grade generative AI product before ChatGPT made LLMs mainstream. The email assistant helped professionals write emails 10x faster using AI.

We joined during a critical growth phase and led the AI backend architecture that powered rapid scaling from 10,000 to 100,000 users. The product's success led to acquisition by MailMerge in 2024.

This was shipping AI features at startup speed while maintaining the reliability that paying customers demanded — no playbook existed for LLM production systems at the time.

What We Built

• Multi-provider LLM orchestration — intelligent routing between OpenAI and Cohere based on task complexity
• Streaming response architecture using Server-Sent Events for real-time text generation
• AI observability infrastructure with Gantry for monitoring output quality and detecting model drift
• Cost optimization systems achieving 40-50% infrastructure savings

Key Achievements

• Scaled AI backend 10x from 10,000 to 100,000 active users
• Reduced infrastructure costs by 40-50% through intelligent model routing
• Maintained 99.9% uptime during rapid growth phase
• Built Chrome Extension backend integrating with Gmail and other clients
• Integrated Stripe payments with multi-currency support

Technical Challenges Solved

• LLM latency optimization — implemented streaming and speculative caching for real-time suggestions
• Cost control with spiky traffic — designed multi-provider architecture with intelligent routing
• AI output quality monitoring — built comprehensive observability for generative AI systems

AI & LLM

• OpenAI GPT-3/3.5
• Cohere
• Gantry (AI Observability)
• Prompt Engineering

Backend

• TypeScript / Node.js
• Python / FastAPI
• GraphQL / gRPC
• Hasura

Data & Messaging

• PostgreSQL
• MongoDB
• Redis
• RabbitMQ / Celery
• BigQuery

Infrastructure

• AWS
• Nomad / NixOS
• Docker
• Terraform
• Lambda