I just finished building a full Instagram DM automation SaaS for a client. Think ManyChat — but built from scratch, for the Indian market. Let me walk you through what went into it. 👇 𝗧𝗵𝗲 𝗰𝗹𝗶𝗲𝗻𝘁'𝘀 𝗿𝗲𝗾𝘂𝗶𝗿𝗲𝗺𝗲𝗻𝘁𝘀 𝘄𝗲𝗿𝗲 𝗰𝗹𝗲𝗮𝗿: • Auto-DM anyone who comments a keyword on a post • Auto-DM story replies and mentions • Referral system — PRO users earn ₹24.75 for every person they refer • Two pricing tiers: Free (₹0) and Creator Pro (₹429/month) • Referred users pay only ₹99 for their first month Simple to describe. Surprisingly nuanced to build correctly. 𝗧𝗵𝗲 𝗽𝗮𝗿𝘁 𝗺𝗼𝘀𝘁 𝗱𝗲𝘃𝘀 𝗴𝗲𝘁 𝘄𝗿𝗼𝗻𝗴 — 𝗜𝗻𝘀𝘁𝗮𝗴𝗿𝗮𝗺 𝗢𝗔𝘂𝘁𝗵: Instagram gives you a token that expires in 1 hour. You must immediately exchange it for a 60-day long-lived token. Then refresh it at day 53. Miss any of this → every automation silently breaks at day 60. No error. Just stopped DMs. I built the full lifecycle: connect → exchange → hash + store → auto-refresh cron → manual refresh UI for users. 𝗧𝗵𝗲 𝗽𝗮𝗿𝘁 𝘁𝗵𝗮𝘁 𝗰𝗼𝘂𝗹𝗱'𝘃𝗲 𝗱𝗮𝗺𝗮𝗴𝗲𝗱 𝘁𝗵𝗲 𝗰𝗹𝗶𝗲𝗻𝘁'𝘀 𝗿𝗲𝗽𝘂𝘁𝗮𝘁𝗶𝗼𝗻: Meta retries webhook delivery 3 times if you don't respond fast enough. Without a deduplication layer, a single comment triggers three identical DMs to the same person. I've seen this happen in production at other companies — users block the account immediately. Solution: a WebhookEvent table with a unique constraint on (provider, messageId). The second insert fails at the database level. No duplicate DMs. Ever. 𝗧𝗵𝗲 𝗿𝗲𝗳𝗲𝗿𝗿𝗮𝗹 𝘀𝘆𝘀𝘁𝗲𝗺 𝗱𝗲𝘁𝗮𝗶𝗹 𝗜'𝗺 𝗽𝗿𝗼𝘂𝗱 𝗼𝗳: The "first-time user only" rule for referral discounts is enforced by a @unique constraint on the referredUserId column — not application code. Even if there's a race condition (two requests hitting the API simultaneously), the database rejects the second insert. No double-discounts possible. This is the difference between a system that works in testing and one that works in production. 𝗙𝘂𝗹𝗹 𝘀𝘁𝗮𝗰𝗸 𝗱𝗲𝗹𝗶𝘃𝗲𝗿𝗲𝗱: Next.js 14 · tRPC · TanStack Query · BetterAuth · Prisma · PostgreSQL · BullMQ · Redis · Recharts This project reminded me why I love freelance work. You're not building a demo. You're building something real people will use, real money will flow through, and real businesses will depend on. That pressure makes you a better engineer. If you're a founder, startup, or business that needs a full-stack SaaS product built with this level of attention to detail — let's talk. Comment below or send me a DM. Always happy to discuss your project. hashtag#Freelancing hashtag#SoftwareDevelopment hashtag#NextJS hashtag#SystemDesign hashtag#SaaS hashtag#FullStack hashtag#TypeScript hashtag#BuildInPublic hashtag#IndianDevelopers