Certified - AWS Certified Cloud Practitioner

A recurring challenge in cloud networking is how to access AWS services or third-party applications without exposing traffic to the public internet. Virtual Private Cloud Endpoints, or VPC endpoints, solve this by providing private connectivity within the AWS network. Instead of routing requests through a NAT Gateway or Internet Gateway, VPC endpoints keep traffic entirely inside AWS’s backbone, reducing exposure and simplifying compliance. This approach not only improves security but often reduces latency and costs, since public internet paths are avoided. AWS PrivateLink builds on this idea by extending private connectivity beyond core AWS services, enabling access to partner and custom applications through private network paths. Together, VPC endpoints and PrivateLink form a cornerstone of secure, private cloud architectures.
There are two main types of VPC endpoints: gateway and interface. Gateway endpoints support S3 and DynamoDB, providing a highly scalable and cost-efficient way to keep traffic private. When configured, route tables are updated so that requests for S3 or DynamoDB are directed to the endpoint instead of going through a NAT Gateway. For example, an analytics application writing logs to S3 can send all requests privately through the gateway endpoint, ensuring no internet exposure. Because S3 and DynamoDB are among AWS’s most commonly used services, providing specialized gateway endpoints allows them to be accessed at scale with minimal complexity. These endpoints are both secure and economical, making them the default choice for their supported services.
Interface endpoints expand this model to other AWS services by deploying Elastic Network Interfaces (ENIs) into subnets. These ENIs act as private access points, each with its own private IP, through which applications connect. For example, an interface endpoint for Amazon SNS allows EC2 instances in a private subnet to publish messages without using an Internet Gateway. Security groups can be applied to these ENIs, adding another layer of control. Because they operate at the network interface level, interface endpoints are more flexible but carry additional cost compared to gateway endpoints. They provide the building block for connecting to a wide range of AWS services, SaaS providers, and even custom applications through PrivateLink.
PrivateLink itself extends the concept of interface endpoints by allowing AWS services or customer applications to be published privately. On the provider side, a Network Load Balancer fronts the service, while on the consumer side, customers create interface endpoints in their VPCs. This creates a secure, private channel without exposing the service publicly. For instance, a SaaS company might offer its application to customers via PrivateLink, ensuring that sensitive data never traverses the internet. This design allows customers to consume third-party services as if they were native AWS services, with all traffic contained within the AWS backbone. PrivateLink thus bridges private networking with external partnerships in a secure, standardized way.
Organizations can also publish their own services via endpoint services. By placing a Network Load Balancer in front of their application and configuring it as an endpoint service, teams can allow other AWS accounts—or even external customers—to connect securely. The provider can require acceptance of connection requests and enforce authentication policies, ensuring only trusted consumers gain access. For example, a central IT team might expose an internal logging service to other business units through PrivateLink. This eliminates the need to manage public endpoints or VPN tunnels, streamlining secure access. Endpoint services turn internal applications into easily consumable, private offerings across account and organizational boundaries.
Security is an integral part of endpoint architecture. Interface endpoints support security groups, allowing administrators to control which resources can connect to the endpoint. Endpoint policies further restrict access, defining which principals can use the endpoint and under what conditions. For example, an endpoint policy might limit S3 access to only a specific bucket or restrict DynamoDB access to certain tables. These policies align with the principle of least privilege, ensuring endpoints don’t inadvertently open broader access than intended. By combining security groups with endpoint policies, organizations achieve both network-level and identity-based controls, creating a layered defense.
DNS plays a central role in how endpoints are consumed. By default, AWS modifies DNS resolution so that requests to service names like s3.amazonaws.com resolve to the endpoint’s private IP. This ensures applications don’t need to change how they connect—they use the same DNS name, but traffic stays inside AWS. For custom or cross-account endpoints, private DNS names can be configured to provide user-friendly naming. Split-horizon DNS may be required in hybrid environments to ensure queries resolve correctly depending on origin. Understanding DNS behavior is crucial, as many endpoint troubleshooting issues stem from resolution mismatches rather than connectivity itself.
To achieve resilience, interface endpoints can be deployed across multiple subnets in different Availability Zones. This zonal redundancy ensures that if one AZ experiences issues, traffic can still route through endpoints in others. For example, deploying endpoints for Amazon Kinesis across three AZs ensures uninterrupted data ingestion even if one zone fails. Gateway endpoints are inherently resilient because they operate at the routing level, but interface endpoints require deliberate multi-AZ planning. By spreading endpoints across subnets, organizations maintain the high availability expected in modern architectures.
Gateway endpoints for S3 and DynamoDB also support endpoint policies for granular control. These policies can restrict which buckets or tables can be accessed, and even enforce specific IAM conditions. For instance, a policy might require that requests include an IAM principal tag matching the project’s name, preventing cross-project data leaks. This ability to control access at the network edge aligns with compliance frameworks, where private data paths must be tightly controlled. Gateway endpoints combine simplicity with policy-driven governance, making them powerful tools for securing common data services.
PrivateLink supports cross-account consumption, enabling one account to publish a service while others access it privately. This reduces the need for internet-exposed APIs or VPN tunnels between accounts. For example, a company with multiple AWS accounts for different business units could centralize a billing service in one account and expose it to others through PrivateLink. Cross-account patterns fit neatly into multi-account strategies, improving both security and manageability. They reinforce the theme of AWS networking: segmentation for control, with flexible private connectivity where needed.
Endpoints are not limited to AWS-native use. With VPN or Direct Connect, on-premises systems can also access AWS services through VPC endpoints. This allows hybrid environments to benefit from private connectivity paths, keeping data secure end-to-end. For example, an on-premises analytics system could ingest data from DynamoDB through a gateway endpoint, avoiding internet exposure entirely. By combining endpoints with hybrid links, enterprises extend their private networks seamlessly into AWS, aligning with compliance and performance goals. This design highlights how endpoints are not just cloud-native tools but hybrid enablers as well.
Pricing for endpoints depends on type. Gateway endpoints for S3 and DynamoDB have no hourly cost, making them highly economical. Interface endpoints, however, incur hourly charges per endpoint per AZ, plus data processing charges for traffic. This means costs scale with both footprint and usage. For example, deploying many interface endpoints across multiple AZs can accumulate costs quickly if not consolidated. Awareness of pricing signals helps organizations design endpoint strategies that balance security with cost efficiency. Endpoints remain cheaper than routing traffic through NAT Gateways for high-volume workloads, but thoughtful planning is essential.
Ultimately, the value of VPC endpoints and PrivateLink lies in reducing the attack surface by keeping traffic private. By eliminating exposure to the public internet, organizations minimize risks of interception, misconfiguration, or attack. For example, a financial services firm processing sensitive transactions benefits from knowing that data never traverses uncontrolled networks. This private-by-default approach not only improves security but also simplifies compliance, since auditors can verify that data paths are restricted to AWS’s backbone. Endpoints turn private access into a default practice rather than an exception, aligning cloud operations with modern security expectations.
For more cyber related content and books, please check out cyber author dot me. Also, there are other prepcasts on Cybersecurity and more at Bare Metal Cyber dot com.
When choosing between gateway and interface endpoints, the decision often comes down to supported services, scale, and cost. Gateway endpoints are limited to S3 and DynamoDB but are highly cost-effective, with no hourly charges. They integrate seamlessly with route tables, making them the default choice when those services are in use. Interface endpoints, on the other hand, cover a much broader set of AWS services and third-party applications but incur hourly and per-GB charges. For example, an analytics workload writing logs to S3 should use a gateway endpoint, while an application needing private access to Amazon SNS or a partner SaaS must use an interface endpoint. Recognizing these distinctions helps architects balance simplicity, cost, and capability.
Restricting S3 access with endpoint policies is a common best practice. By attaching a policy to a gateway endpoint, organizations can ensure that traffic only flows to approved buckets and only from specific IAM principals. Condition keys further refine control, such as requiring requests to originate from a particular VPC or tagged role. For example, a company might restrict access so only the finance bucket is reachable through the endpoint, blocking other S3 usage. This approach enforces least privilege not just at the IAM level but also at the network level, preventing accidental or unauthorized data movement. It illustrates how endpoint policies combine network routing with identity governance.
Centralized endpoint strategies improve efficiency in large organizations. Instead of deploying interface endpoints in every VPC, some enterprises create a dedicated “endpoint VPC” and share it with other accounts using AWS RAM. Applications in different VPCs can then route traffic privately through this central VPC to reach AWS services. For example, a shared services account might host endpoints for KMS, CloudWatch, and SNS, avoiding duplication across dozens of application accounts. This design reduces cost and operational overhead while maintaining private connectivity. It highlights how endpoints integrate with AWS’s multi-account strategies to provide both economy and governance.
Publishing your own services through PrivateLink enables secure consumption across accounts or even customers. By fronting an application with a Network Load Balancer and designating it as an endpoint service, providers can offer private access points. Consumers then create interface endpoints in their own VPCs to connect. Acceptance rules and optional IAM-based authentication ensure only authorized consumers can connect. For example, a fintech company could offer its API privately to customers via PrivateLink, keeping all traffic on AWS’s backbone. This eliminates the need for public IPs, firewalls, or cross-account VPNs, transforming private services into first-class cloud-native offerings.
DNS behavior often requires careful planning when endpoints are involved. By default, AWS modifies DNS so that requests to service domains resolve to private IPs associated with endpoints. However, in hybrid environments with on-prem resolvers, split-horizon DNS may be needed to ensure internal and external queries resolve appropriately. For example, without correct forwarding, an on-premises system might resolve s3.amazonaws.com to a public endpoint rather than the gateway endpoint inside AWS. Aligning DNS configurations ensures that applications consistently use private paths, preventing leakage onto the public internet. It reinforces the idea that endpoints and DNS must be designed together for a seamless experience.
Private SaaS connectivity is one of PrivateLink’s most compelling use cases. SaaS providers publish services as endpoint offerings, and customers connect privately through interface endpoints. This removes the need for customers to whitelist public IP ranges or manage VPN tunnels. For example, a security monitoring provider might offer PrivateLink connectivity, allowing customers to send logs without exposing sensitive data to the internet. This model strengthens trust, simplifies onboarding, and aligns SaaS consumption with enterprise security expectations. It demonstrates how PrivateLink extends AWS’s private connectivity philosophy beyond its own services to the wider partner ecosystem.
One of the strongest security arguments for endpoints is that they eliminate the need for Internet Gateways or NAT Gateways for accessing AWS services. By routing traffic privately, instances in private subnets can access services like S3, DynamoDB, or CloudWatch Logs without ever being exposed. For example, a private database cluster can write backups directly to S3 via a gateway endpoint, with no route to the public internet. This design drastically reduces the attack surface, aligning with zero-trust principles by ensuring resources have no unnecessary external connectivity. Endpoints turn private-only architectures into a standard rather than a special case.
Monitoring and observability are integral to operating endpoints. CloudWatch provides metrics on connection counts, bytes processed, and error rates, while VPC Flow Logs can confirm whether traffic is using endpoints or public paths. For example, if an application unexpectedly hits a NAT Gateway, flow logs may reveal that DNS resolution bypassed the endpoint. Proactive monitoring ensures endpoints fulfill their purpose, avoiding both security risks and unnecessary costs. Administrators can set alarms to detect unusual spikes in endpoint usage, catching misconfigurations or potential abuse early. Observability thus transforms endpoints from hidden plumbing into visible, manageable infrastructure.
Cost optimization requires thoughtful endpoint placement and consolidation. Because interface endpoints incur hourly fees per AZ, duplicating them across many VPCs can become expensive. Centralized endpoint VPCs or shared endpoints help control costs while maintaining coverage. Monitoring data transfer charges also matters, as high-volume services can generate significant expenses. For example, logging thousands of CloudWatch events per second through endpoints can drive up costs if not budgeted. By consolidating and forecasting usage, organizations ensure endpoints deliver security without becoming cost burdens. Balancing least-privilege design with economic efficiency remains a core theme in cloud networking.
Troubleshooting endpoint issues often comes down to DNS, security groups, or routes. If traffic is not flowing, checking whether DNS resolves to the private IP of the endpoint is the first step. Next, security group rules on the endpoint ENI must allow the intended traffic. Finally, route tables must direct requests through the endpoint. For example, if an EC2 instance cannot reach DynamoDB despite an endpoint, a misconfigured DNS resolver or missing SG rule could be the culprit. By methodically checking these layers, administrators can resolve issues quickly. Endpoint troubleshooting reinforces the principle that networking and identity controls must align perfectly.
Compliance is another key benefit of endpoints. By keeping data paths private, organizations can demonstrate to regulators that sensitive information never traverses the public internet. Endpoint logs and policies provide auditable evidence of restricted access. For example, a healthcare provider can prove that patient data written to S3 only passed through a gateway endpoint, aligning with HIPAA requirements. This compliance posture reduces risk while easing audit burdens. Endpoints thus provide not only security and performance but also governance benefits, making them critical in regulated industries.
Multi-Region strategies extend endpoint benefits globally. Endpoints must be created in each Region where services are consumed, and policies can enforce consistent access across them. For example, a multinational company might deploy interface endpoints for KMS in both Europe and North America to ensure encryption keys remain locally accessible. While this adds cost, it ensures resilience and compliance with regional data sovereignty rules. Multi-Region planning highlights that endpoints are not just local optimizations but global design considerations, supporting enterprises operating across jurisdictions.
From an exam perspective, endpoints serve as the clear answer whenever private access to AWS services is required. Scenarios that mention avoiding Internet Gateways, NAT Gateways, or public IPs should point directly to VPC endpoints. Gateway endpoints apply to S3 and DynamoDB, while interface endpoints extend to other services and PrivateLink SaaS offerings. Keywords like “private connectivity,” “no internet,” or “cross-account private access” are strong signals. For learners, mapping these cues ensures confidence in selecting endpoints as the right tool.
In conclusion, VPC endpoints and PrivateLink provide private, secure pathways to AWS services and partner applications. Gateway endpoints simplify access to S3 and DynamoDB at scale, while interface endpoints extend private connectivity across the AWS ecosystem. PrivateLink enables organizations to publish and consume services without internet exposure, transforming private access into a standardized cloud pattern. With careful design, monitoring, and cost governance, endpoints strengthen both security and compliance while simplifying architecture. The lesson for both exam prep and real-world design is clear: prefer endpoints to keep traffic private, reduce attack surfaces, and align connectivity with modern zero-trust principles.