Private Connectivity Design

Enterprise AWS environments with hundreds of accounts and thousands of microservices face a fundamental architectural tension: services must communicate across account boundaries, yet every path traversing the public internet introduces attack surface, compliance risk, and operational overhead. The SAP-C02 exam consistently rewards designs that eliminate internet traversal while preserving strict producer-consumer isolation. This lesson establishes the architectural patterns that replace NAT gateways, internet gateways, and public endpoints with private connectivity constructs operating entirely within the AWS network backbone.

Introduction to private connectivity

Traditional cross-account communication often relies on public IP addresses, NAT gateways routing through internet gateways, or VPN tunnels that add latency and management burden. Each of these patterns exposes traffic to potential interception, requires security group rules accommodating public CIDR ranges, and creates dependencies on internet availability for internal service communication. The Well-Architected Framework security pillar explicitly calls for minimizing attack surface, and SAP-C02 scenarios penalize architectures that default to internet-routed paths when private alternatives exist.

Private connectivity in AWS rests on three pillars that address distinct architectural requirements:

• AWS PrivateLink enables service-to-service communication across accounts and organizations without VPC peering, route table manipulation, or CIDR coordination between producer and consumer.

• VPC endpoints provide private access to AWS service APIs, ensuring that calls to S3, DynamoDB, Secrets Manager, and more than 100 other services never leave the AWS network.

• Endpoint policies enforce granular traffic governance at the network layer, restricting which principals and resources can be accessed through each endpoint, regardless of IAM permissions.

These patterns apply across multi-account Organizations, SaaS integrations where third-party providers expose services privately, and hybrid architectures where on-premises systems reach AWS services through Direct Connect without internet backhauling. Private DNS resolution through Route 53 ensures applications use standard service endpoints without code changes, maintaining operational simplicity alongside security enforcement.

The following diagram contrasts traditional public connectivity with the PrivateLink-based private pattern that SAP-C02 expects architects to prefer.

With this foundation established, the next section examines how PrivateLink implements the producer-consumer model that eliminates the architectural compromises of traditional connectivity.

AWS PrivateLink and VPC endpoint services

Producer-consumer architecture

AWS ...