Creates subnets from a map variable keyed by region/name. Accepts secondary ranges, flow logs, purpose, role, and IPv6 options. Uses for_each on the subnet map with resource-level count for conditional flow_logs. The design is clean and extensible; adding new subnet features (e.g., ip_collection) requires only expanding the variable schema and adding a single dynamic block. This pattern is directly reusable for any Terraform project that needs to manage a variable number of similarly-structured resources.

Manages classic GCP firewall rules using separate ingress_rules and egress_rules maps, each supporting allow/deny rules with logging. Deprecated firewall_rules variable is still supported by converting to the new format. Uses dynamic blocks for allow, deny, and log_config. The decoupling of ingress and egress into distinct maps simplifies rule configuration and reduces errors. The deprecation pattern (mark old variable as deprecated, transform inputs) is a robust way to manage API churn in Terraform modules.

Creates a GCP VPC with many optional features controlled by boolean variables (auto_create_subnetworks, delete_default_routes_on_create, enable_ipv6_ula, network_profile, bgp_best_selection, etc.). Uses conditional resource creation via count and inline logic to set fields like routing_mode and mtu. The pattern of exposing a rich set of feature flags while maintaining a clean interface demonstrates good Terraform module design. It can be extracted as a standalone VPC module.