When should I use VPC Peering?

Choose VPC Peering for a small number of VPCs (2-5) needing simple point-to-point connectivity. It has no hourly charge (data transfer only) and no transitive routing.

When should I use Transit Gateway?

Choose Transit Gateway for many VPCs needing full mesh connectivity, centralized VPN/Direct Connect, shared services VPC, and network segmentation with route tables. Supports transitive routing.

When should I use AWS PrivateLink?

Choose PrivateLink to expose a specific service to other accounts/VPCs without full network access, when you have overlapping CIDRs, or for zero-trust architecture with minimal exposure.

AWS Transit Gateway vs VPC Peering vs PrivateLink

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Transit Gateway vs VPC Peering vs PrivateLink Comparison

When to Choose Which

AWS Certification Exam Practice Questions

AWS provides multiple VPC connectivity options, each designed for different network topologies and use cases.

VPC Peering is point-to-point, Transit Gateway is a hub for many-to-many connectivity, and PrivateLink is for private service access without network exposure.
Choice depends on number of VPCs, routing requirements, security posture, and cost.

Transit Gateway vs VPC Peering vs PrivateLink Comparison

Feature	VPC Peering	Transit Gateway	PrivateLink
Topology	Point-to-point (1:1)	Hub-and-spoke (many:many)	Service endpoint (consumer:provider)
Transitive Routing	No	Yes	No (service access only)
Scale	125 peering connections per VPC	5,000 attachments per TGW	Unlimited endpoints
Cross-Region	Yes (inter-region peering)	Yes (inter-region peering)	Yes (with inter-region support)
Cross-Account	Yes	Yes (RAM sharing)	Yes
CIDR Overlap	Not allowed	Not allowed (per attachment)	Allowed (uses ENI in consumer VPC)
Network Exposure	Full VPC network visible to peer	Full VPC network via route tables	Only the service endpoint exposed
Bandwidth	No limit (same as inter-AZ)	Up to 50 Gbps per attachment	Up to 100 Gbps per endpoint
Cost	Data transfer only (no hourly charge)	Hourly per attachment + data processing	Hourly per endpoint + data processing
Use Case	Few VPCs, simple connectivity	Many VPCs, centralized routing, VPN/DX aggregation	Expose service privately, SaaS connectivity, zero-trust
Route Management	Update route tables in both VPCs	Centralized route tables on TGW	No route table changes needed
Security	Security groups + NACLs	Security groups + NACLs + TGW route tables	Minimum exposure (only service port)

When to Choose Which

Choose VPC Peering – Small number of VPCs (2-5), simple point-to-point connectivity, lowest cost, no transitive routing needed.
Choose Transit Gateway – Many VPCs needing full mesh connectivity, centralized VPN/Direct Connect, shared services VPC, network segmentation with route tables.
Choose PrivateLink – Expose a specific service to other accounts/VPCs without full network access, overlapping CIDRs, SaaS service consumption, zero-trust architecture.

Combine TGW + PrivateLink – Transit Gateway for general connectivity between VPCs, PrivateLink for specific service access with minimal exposure.

AWS Certification Exam Practice Questions

A company has 50 VPCs that all need to communicate with a shared services VPC and a centralized Direct Connect connection. Which connectivity solution scales best?
1. VPC Peering (50 connections)
2. Transit Gateway
3. PrivateLink
4. VPN to each VPC
A SaaS provider needs to expose their service to customers in different AWS accounts without exposing their entire VPC network. The customer VPCs have overlapping CIDR ranges. Which solution works?
1. VPC Peering
2. Transit Gateway
3. PrivateLink
4. Site-to-Site VPN

Two VPCs in the same region need connectivity. The traffic volume is minimal, cost is a priority, and no transitive routing is needed. What is the most cost-effective solution?
1. Transit Gateway
2. VPC Peering
3. PrivateLink
4. AWS Cloud WAN
An organization needs VPC A to route traffic through VPC B to reach VPC C. Which service supports this transitive routing?
1. VPC Peering
2. PrivateLink
3. Transit Gateway
4. Internet Gateway