https://aayushgoel.dev/blog/ Notes on backend systems that have to survive production — ERP integration, messaging infrastructure, and the unglamorous work of making them reliable. en mail@aayushgoel.dev (Aayush Goel) mail@aayushgoel.dev (Aayush Goel) Mon, 21 Sep 2026 09:00:00 +0530 https://aayushgoel.dev/blog/multi-tenant-whatsapp-cloud-api.html https://aayushgoel.dev/blog/multi-tenant-whatsapp-cloud-api.html Mon, 21 Sep 2026 09:00:00 +0530 mail@aayushgoel.dev (Aayush Goel) Engineering A WhatsApp webhook gives you a number and a person, and neither is a tenant. Separating store visibility from store registration, why the session key has to be compound, and caching the retailers who do not exist. https://aayushgoel.dev/blog/tally-erp-two-way-sync.html https://aayushgoel.dev/blog/tally-erp-two-way-sync.html Mon, 21 Sep 2026 09:00:00 +0530 mail@aayushgoel.dev (Aayush Goel) Engineering Tally has no REST API, answers HTTP 200 on failure, and its documented batching is a no-op. What two generations of sync taught me.