How I Built an API-First Zapier Alternative (And Why Developers Need It)

Lee — Mon, 15 Dec 2025 20:32:19 +0000

How I Built a Complete API-First Automation Platform in 6 Days

TL;DR: Built SiloWorker (https://siloworker.dev) - a full-stack automation platform with 9 tool types, visual workflow builder, and enterprise monitoring. Here's how I
did it in under a week.

What I Actually Built

In just 6 days, SiloWorker went from idea to production-ready automation platform that can genuinely compete with Zapier.

The Complete Feature Set

9 Built-in Tool Types:
• HTTP - Full REST API calls with custom headers/auth
• SendGrid - Email automation with templating

• Twilio - SMS automation with BYOC support
• Database - Direct PostgreSQL queries and operations
• LLM - OpenAI/Anthropic integration for AI workflows
• Webhook - Outbound webhooks with signature verification
• Transform - Data manipulation and formatting
• Conditional - Complex branching logic with expressions
• Delay - Timing controls for workflow orchestration

Visual Workflow Builder:
javascript
// React-based drag-and-drop interface
nodes={workflow.nodes}
connections={workflow.connections}
onSave={updateAgent}
/>

10+ Pre-built Templates:
• Lead Notification (Form → Email + Slack)
• Customer Onboarding sequences
• Daily Market Reports with LLM
• AI Content Approval workflows
• API Health Monitoring
• Invoice Reminders
• Database Sync operations
• Webhook Routing
• Batch Data Processing

The "API-First Client" Approach

Here's the key insight: I built the web UI as the first client of my own API. Every dashboard feature uses the same REST endpoints customers would use.

javascript
// The UI is just an API client
const createAgent = async (agentData) => {
const response = await fetch('/v1/agents', {
method: 'POST',
headers: { 'Authorization': Bearer ${apiKey} },
body: JSON.stringify(agentData)
});
return response.json();
};

This forced me to make the API actually usable. If I couldn't build a good UI with it, neither could customers.

Production-Grade in 6 Days

The Stack

Backend: Node.js + Express + PostgreSQL + Redis + BullMQ
Frontend: React + Vite + TailwindCSS
Deployment: Railway with auto-deploy from GitHub
Monitoring: Prometheus + Winston structured logging

Enterprise Features

• Correlation IDs for request tracing
• Deep health checks (DB, Redis, queue status)

• Usage notifications at 80%, 90%, 95% limits
• Graceful shutdowns for zero-downtime deploys
• BYOC fairness - unlimited usage with your own keys
• Production API keys (sk_live_ vs sk_test_)

The BYOC Breakthrough

Most automation tools charge you twice for BYOC: your API costs + platform quotas.

SiloWorker's approach:
javascript
// Only count platform usage, not BYOC
const usingPlatformCredentials = !step.config.api_key && !workspace.sendgrid_api_key;
if (usingPlatformCredentials) {
// Check quotas and count usage

} else {
// BYOC: unlimited usage, no quota counting
}

Result: BYOC users get unlimited email/SMS on any plan.

The Numbers

6 days development (Dec 9-15, 2025)

~8,800 lines of code (4,996 backend + 3,811 frontend)

9 tool types with full configuration

10+ pre-built templates

Complete React dashboard (12 pages)

200+ integration tests

Production monitoring stack

5 pricing tiers with usage tracking

How I Moved So Fast

1. API-First Architecture

Building the UI forced good API design. Every endpoint had to be clean enough for React components.

2. Template-Driven Development

Instead of building tools in isolation, I built complete workflow templates. This revealed missing features immediately.

3. Production from Day 1

Deployed to Railway on day 1. Every feature went straight to production with monitoring.

4. Integration Tests as Documentation

Tests became the spec. If it passed tests, it was ready for users.

What's Next

The platform is live at https://siloworker.dev and accepting users.

Gathering feedback via this form: https://docs.google.com/forms/d/e/1FAIpQLSfxYgd7kDbTiWihNN-mQWzFPkFDEk2YpfV_RMmKAqsb6kaNog/viewform

Pricing: Free tier (200 runs/month), paid plans from $19/month

BYOC: Unlimited email/SMS when you bring your own keys

The complete stack is API-first, but the visual builder makes it accessible to non-developers too. Built in 6 days, ready to compete with tools that took years.

Try it out and let me know what you think! Always interested in feedback from technical teams.

DEV Community: Lee