Mass Video Posting API Tool for Instagram

We’re looking to develop a web-based platform similar to Publer, but specifically designed for mass posting of videos to multiple Instagram accounts (dozens or hundreds) simultaneously.
This will be an internal tool focused on performance, scalability, and API-compliant publication through Instagram Graph API (without Facebook Pages).

I can share a video of how Publer works if needed for better reference.

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Core Features Required:

1. Authentication & User Dashboard
• User registration/login
• Simple and clean dashboard
• Ability to connect and manage multiple Instagram accounts

2. Instagram Account Integration
• Connect accounts using official Instagram Graph API (no Facebook Page required)
• Secure storage and handling of session data, tokens, etc.

3. Video Upload & Management
• Upload videos up to 100–200MB
• Bulk assignment of one video to multiple accounts
• Schedule posts with specific date/time
• Support for auto-posting / delayed publishing

4. Mass Publishing Engine
• Publish one video to many accounts at once or in sequential batches
• Add title, description, hashtags, and custom thumbnails
• Show success/failure notifications per account

5. Post Tracking & Logs
• Action history per account
• Status logs: published / error / pending

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Requirements:
• System must scale to 100+ Instagram accounts
• Strong focus on security, reliability, and failover handling
• Modern stack (preferably Node.js or Python backend, but open to suggestions)

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What We Expect From You:
• Knowledge of load balancing, API rate limits, and multi-threaded publishing
• Proven ability to build scalable posting systems
• Portfolio of similar automation or social media tools (if available)
• Estimated timeline, budget, and phased development (e.g., MVP → scaling)