Warmbly

Email warmup and cold email platform.

Overview

Warmbly is a microservices-based platform for email warmup and cold outreach. It supports Gmail (via API) and IMAP/SMTP providers, with real-time event streaming, distributed workers, and comprehensive tracking.

Architecture

The Frontend (React) connects to three backend services: the Backend API (Go, :8080), Realtime (Elixir/Phoenix, :4000), and Tracking (Rust, :3000).

All three services publish events to Kafka (with Avro/Schema Registry). The Realtime service also uses Google Pub/Sub for cross-node message fanout.

Downstream from Kafka, the Consumer (Go) processes tracking events and the Worker (Go, 1 per machine) handles email operations. Both read/write to PostgreSQL, Redis, and Cassandra (DataStax Astra).

Tech Stack

Component	Technology
Backend API	Go 1.25, Gin
Consumer	Go, Kafka consumer
Worker	Go, distributed (1 per machine)
Tracking	Rust, Axum
Realtime	Elixir 1.18, Phoenix Channels
Message Queue	Confluent Kafka with Avro/Schema Registry
Primary Database	PostgreSQL 16 (AWS RDS)
Time-series	DataStax Astra (Cassandra)
Cache	Redis 7
Object Storage	AWS S3
Pub/Sub	Google Cloud Pub/Sub
Task Queue	Google Cloud Tasks

Services

Service	Port	Description
Backend	8080	REST API, authentication, business logic
Tracking	3000	Pixel tracking and click tracking
Realtime	4000	WebSocket gateway for real-time events
Consumer	-	Kafka event consumer, processes tracking events
Worker	-	Distributed worker for email operations

Quick Start (Development)

Prerequisites

• Docker and Docker Compose
• Go 1.25+ (for local development)
• Rust (for tracking service)
• Elixir 1.18+ (for realtime service)

Start with Docker Compose

cd deploy/docker

# Start infrastructure only (database, redis, kafka)
docker-compose up -d postgres redis kafka schema-registry

# Start all services
docker-compose up

Service URLs (Local)

• Backend API: http://localhost:8080
• Tracking: http://localhost:3000
• Realtime: http://localhost:4000
• Mailpit (email inbox): http://localhost:8025
• Schema Registry: http://localhost:8081
• PostgreSQL: localhost:5432
• Redis: localhost:6379
• Kafka: localhost:9092

Project Structure

• cmd/ — Service entrypoints: backend/, consumer/, worker/
• internal/ — Core Go code:
  • api/ — HTTP handlers
  • app/ — Application services (auth, email, campaign, etc.)
  • config/ — Configuration loading (env vars + AWS Secrets Manager)
  • events/ — Kafka event schemas
  • infrastructure/ — Database, cache, and queue clients
  • models/ — Domain models
  • notify/ — Email notification service and templates
  • pkg/ — Internal packages (emsg, crypto, etc.)
  • repository/ — Data access layer
• tracking/ — Rust tracking service (Axum)
• realtime/ — Elixir WebSocket service (Phoenix Channels)
• web/ — React frontend
• deploy/ — Docker Compose, Dockerfiles, Kubernetes manifests
• resources/ — Technical documentation

Documentation

• Local Development - Docker Compose setup for local development
• Deployment Guide - Step-by-step deployment instructions
• CI/CD Pipeline - CI/CD technical details
• Architecture - System architecture overview
• Events - Kafka event system
• EMSG Format - Email message blob format
• Gmail Integration - Gmail API usage
• IMAP Integration - IMAP/SMTP integration

Building

# Go services (from root)
go build -o bin/backend ./cmd/backend
go build -o bin/consumer ./cmd/consumer
go build -o bin/worker ./cmd/worker

# Tracking service
cd tracking && cargo build --release

# Realtime service
cd realtime && mix deps.get && mix release

CI/CD Pipeline

Warmbly uses GitHub Actions for CI/builds and GitOps for deployments.

PRs trigger CI (tests, linting, security scan). Merging to main builds and pushes Docker images. Tagging a release (v*.*.*) triggers a production deploy via ArgoCD.

Workflow	Trigger	Purpose
ci.yml	PR/Push	Tests, linting, security scan
build-push.yml	Push to main	Build & push Docker images
release.yml	Tag v*.*.*	Build release images (triggers prod deploy)

License

Licensed under the Apache License 2.0.

Copyright 2026 Mindroot Ltd

Full license: LICENSE