When you become dependent on a specific cloud provider's proprietary services and switching to another provider becomes difficult or expensive. Like building your house with custom parts that only work with one supplier.
Using AWS-specific services like DynamoDB and Lambda heavily can create vendor lock-in, making it costly to move to Azure or Google Cloud later.
Vendor lock-in is a business/architecture risk rather than a single cloud service. It happens when your app relies on provider-specific APIs, managed services, tooling, or contracts that are hard to replace. All major clouds can create lock-in through proprietary databases, serverless runtimes, IAM models, networking constructs, observability stacks, and marketplace licensing.