Risu Solutions Built a Self-Hostable Email API Using Only MongoDB (No Redis, No Queues)

Most email APIs today are powerful—but also over-engineered.

Across many existing solutions, a common pattern appears:

Redis for queues
Background workers
Complex retry systems
Multiple services just to send a single email

This works well at scale—but can be heavy and complex for startups and small teams.

So the question becomes:

Can a simple, scalable email API be built using just MongoDB?

That’s the idea behind Risu Mail.

🚨 The Problem with Existing Email APIs

Developers using platforms like SendGrid or Mailgun often face:

Difficulty in self-hosting
Increasing costs at scale
Limited control over data
Complex customization workflows

And when building an in-house solution, it often turns into:

“Add Redis… add queues… add workers… add retry systems…”

At that point, the focus shifts from building features to managing infrastructure.

💡 The Approach: Simplicity First

Instead of adding more components, the system is designed by removing unnecessary ones.

Core idea:
Use MongoDB as the central layer for:

Email storage
Queue handling
Status tracking
Retry logic

No Redis. No external queue system.

🏗️ Architecture Overview

1. Email Creation

When a request is received:

Email data is stored in MongoDB
Status is set to pending
{
to: "[e-mail]",
subject: "Welcome!",
status: "pending",
attempts: 0,
createdAt: new Date()
}

1. Worker Process (Polling-based)

Instead of queues, a worker process runs at intervals:

const emails = await db.emails.find({
status: "pending"
}).limit(10);

Then:

Emails are sent
Status is updated → sent or failed

1. Retry Logic

If sending fails:

if (email.attempts < 3) {
// retry later
} else {
// mark as failed
}

Simple and predictable behavior without external dependencies.

1. Scaling

Scaling remains straightforward:

Multiple workers can run in parallel
MongoDB manages concurrency
Indexing ensures performance
⚙️ Features

Risu Mail is designed beyond just sending emails:

✅ Transactional emails (OTP, alerts, notifications)
✅ Campaign support (bulk emails)
✅ Template system
✅ Email logs & tracking
✅ Simple REST API
🧠 Key Insights

1. Redis is not always required

For many use cases, MongoDB can effectively handle queue-like behavior.

1. Simplicity improves speed

Less infrastructure leads to faster development and easier maintenance.

1. Developers want control

Self-hosting is increasingly important for:

Privacy
Cost efficiency
Flexibility
⚖️ Trade-offs

This architecture is not designed for every scenario.

Limitations:

Polling is less efficient than dedicated queues
Not optimized for extremely high-scale workloads
Requires proper indexing and monitoring

Best suited for:

Startups
Indie developers
MVPs
🚀 About Risu Mail

Risu Mail — Open-source transactional email API with campaigns, OTP, and templates.risu mail

Built for:

Teams that want full control
Developers who prefer self-hosted solutions
Products that need a simpler email infrastructure
🔥 What’s Next

Upcoming improvements include:

Web dashboard
Advanced analytics
Plugin ecosystem
🙌 Feedback

Feedback and discussions are always welcome:

Would this approach work for your use case?
What features would you expect from a self-hosted email API?
What challenges exist in your current email setup?

Let’s build better developer tools together 🚀