The primary differences between VPC Peering, PrivateLink, and VPC Endpoints in AWS revolve around their use cases, the way they facilitate communication, and their configuration requirements. Here's a basic breakdown of each:
VPC Peering
Use Case: VPC Peering is used to connect two VPCs to enable communication between them as if they are part of the same network. Communication: Direct, private IP connectivity between VPCs. Configuration: A peering connection is established, and route tables are updated to direct traffic between the VPCs. Scalability: Each VPC Peering connection is one-to-one. For a mesh network, multiple peering connections are required. Transitive Peering: Not supported. Traffic cannot be routed from one peered VPC to another indirectly. PrivateLink
Use Case: PrivateLink is used to provide private access to services hosted on AWS without exposing traffic to the public internet. Often used for SaaS applications. Communication: Uses endpoint services (powered by Network Load Balancer) and interface endpoints to connect to services privately. Configuration: Service provider creates an endpoint service, and service consumers create an interface endpoint in their VPC to connect to the service. Scalability: Allows one-to-many and many-to-one communication. Multiple consumers can connect to a single service provider. Transitive Peering: Not applicable as it is service-based connectivity rather than VPC-to-VPC. VPC Endpoints
Use Case: VPC Endpoints are used to privately connect your VPC to supported AWS services without requiring an internet gateway, NAT device, VPN connection, or AWS Direct Connect. Interface Endpoints: Use elastic network interfaces (ENIs) with private IPs in the VPC subnet. Gateway Endpoints: Use route tables to direct traffic to AWS services like S3 and DynamoDB. Communication: Private connectivity to AWS services. Interface endpoints use ENIs, and gateway endpoints use route tables. Configuration: Create endpoints in the VPC and update route tables (for gateway endpoints) or security groups (for interface endpoints). Scalability: Highly scalable as they are designed to handle traffic to and from AWS services. Transitive Peering: Not applicable as they connect VPCs to AWS services rather than VPC-to-VPC. Key Differences
VPC Peering: Connects two VPCs for internal communication. PrivateLink: Provides private access to services across different VPCs and AWS accounts. VPC Endpoints: Connects VPCs to AWS services privately. VPC Peering: Direct VPC-to-VPC communication. PrivateLink: Service-based, not VPC-to-VPC, uses endpoint services and interface endpoints. VPC Endpoints: Service-based, either interface (using ENIs) or gateway (using route tables). Configuration Requirements: VPC Peering: Peering connection and route table updates. PrivateLink: Endpoint service creation and interface endpoint configuration. VPC Endpoints: Creation of endpoints and possibly route table/security group updates. Scalability and Flexibility: VPC Peering: Limited by the number of peering connections and complexity increases with a large number of VPCs. PrivateLink: Scalable, one service can be accessed by multiple consumers. VPC Endpoints: Scalable for connecting VPCs to multiple AWS services efficiently. 
Difference between VPC Peering, PrivateLink, and VPC Endpoints