Case Study · Full-Stack Platform

CodEven: Modern Multi-Tenant Business Automation for Turkish SMBs

How two co-founders built a production multi-tenant SaaS platform integrating WhatsApp Cloud API, Instagram messaging, calendar scheduling, and AI voice telephony using AI coding tools.

1. The Problem

Small business owners in Turkey often struggle with disjointed customer operations: answering customer inquiries manually across WhatsApp and Instagram, keeping appointments on paper or Excel sheets, missing calls during busy hours, and handling payment renewals separately. Off-the-shelf enterprise suites are too complex and expensive, while isolated single-purpose bots fail to keep appointments, customer records, and communication history in sync.

2. What We Built

We engineered CodEven—a unified, multi-tenant business operating platform tailored for service-based businesses:

Unified Messaging Channels

Integrated WhatsApp Cloud API and Instagram Messaging via Meta Tech Provider status and Meta Embedded Signup for customer onboarding.

Instagram DM & Comment Automation

Automated response bots handling incoming Instagram direct messages and public comments with quota controls.

Concurrency-Safe Appointment Engine

Real-time calendar scheduling with strict concurrency slot locking, automatic confirmation, and customer notifications.

AI Voice Telephony Receptionist

Retell AI integration that answers business calls, checks free calendar slots, and books appointments directly into the calendar.

Platform Security & Billing

AES-256-GCM token encryption for third-party credentials, Iyzico subscription billing, and HubSpot CRM OAuth sync.

Mobile Companion & Multilingual Support

A Capacitor mobile client and 4-language localization (Turkish, English, German, French).

3. How It Works (Architecture)

A modular, cloud-native architecture connecting customer channels with a robust backend engine:

Client Applications

Next.js 15 Web AppCapacitor Mobile (iOS/Android)i18n (TR / EN / DE / FR)

↓ Secure APIs & Webhooks

Communication Channels

WhatsApp Cloud API (Embedded Signup)Instagram Messaging & DM BotsRetell AI Telephony Webhooks

↓ Concurrency Locks & Workflows

Core Business Engine

Appointment Concurrency EngineNotification DispatcherIyzico Recurring SubscriptionsHubSpot OAuth Syncn8n Automation Engine

↓ Encrypted Storage & Guardrails

Data & Security Layer

PostgreSQL (Neon) + Prisma ORMUpstash Redis (Rate Limiting & Cache)AES-256-GCM Token Encryption~50 Automated Contract Tests

4. Results & Engineering Facts

✓End-to-end built and shipped to production by two co-founders pairing with AI coding agents.
✓Complete multi-tenant SaaS platform deployed live on Vercel with serverless compute.
✓Attained official Meta Tech Provider status with WhatsApp Cloud API Embedded Signup.
✓~50 contract tests covering business logic, API contracts, quotas and security gates.

5. Technology Stack

Frontend & Mobile

Next.js 15 App RouterReactTypeScriptTailwind CSSCapacitor (iOS & Android)

Backend & Data

PostgreSQL (Neon)Prisma ORMUpstash RedisVercel Serverless

Telephony & AI

Retell AI VoiceElevenLabsn8n Workflow AutomationGemini

Platform & Security

Meta Tech ProviderWhatsApp Cloud APIInstagram Graph APIAES-256-GCMIyzicoHubSpot OAuth

Need a full-stack platform or custom AI integration?

Let's discuss your project architecture, AI voice receptionists, or Meta platform onboarding.

Get in touch →