Build a Serverless API with Azure Functions and Cosmos DB | Step-by-Step Tutorial

No servers, no problem. In this step-by-step tutorial, we build a real serverless API on Azure: Azure Functions handles the compute, Azure Cosmos DB stores the data. You will learn how HTTP triggers and bindings wire everything together, which hosting plan to pick, how request units and the partition key work in Cosmos DB, and the exact build steps — plus cost and production best practices. What you'll learn: Why a serverless API: no servers to manage, automatic scale, pay only for execution time The architecture: client → HTTP trigger → input binding → your code → output binding → response Triggers and bindings: exactly one trigger per function; declarative input/output bindings, no SDK boilerplate Hosting plans: Consumption vs Flex Consumption vs Premium vs Dedicated — and which to pick Cosmos DB essentials: containers, the partition key (chosen once, forever), request units (RU/s) The code: HTTP trigger + Cosmos DB input/output bindings in function.json Deploy and verify: Function App, Cosmos DB account, app settings, Postman test, Data Explorer check Cost: Consumption free grant (1M executions + 400,000 GB-s/month), Cosmos DB free tier (1,000 RU/s + 25 GB) Five production practices: managed identity, partition-key design, auth levels, cold starts, Application Insights Timestamps (bookended video, 7:19 total): 0:00 — Intro bumper 0:06 — Welcome: build a serverless API 0:29 — What we are building 0:54 — In this video 1:16 — How the serverless API works 1:40 — Triggers and bindings 2:07 — Functions hosting plans 2:37 — Azure Cosmos DB at a glance 3:03 — Request units and the partition key 3:31 — Build steps 3:56 — Bindings in function.json 4:22 — The request flow 4:54 — What it costs 5:17 — Five production practices 5:48 — Key takeaways 6:18 — Subscribe 6:35 — Outro end card If this helped, subscribe to EduTechGyan for daily Azure, AWS, GCP, and AI videos — and turn on the bell so you never miss the next tutorial. Official sources: Azure Functions triggers and bindings: https://learn.microsoft.com/en-us/azu... Azure Functions scale and hosting (Consumption, Flex Consumption, Premium, Dedicated): https://learn.microsoft.com/en-us/azu... Azure Cosmos DB input binding for Functions: https://learn.microsoft.com/en-us/azu... Azure Cosmos DB output binding for Functions: https://learn.microsoft.com/en-us/azu... Azure Cosmos DB databases, containers, and items: https://learn.microsoft.com/en-us/azu... Azure Cosmos DB partitioning and horizontal scaling: https://learn.microsoft.com/en-us/azu... Azure Cosmos DB service quotas and limits: https://learn.microsoft.com/en-us/azu... #AzureFunctions #CosmosDB #Serverless #AzureTutorial #EduTechGyan