Architecture comparison
DevTools
GitLab.com is primarily hosted on Google Cloud Platform in the us-east1 region, with most application services running on multiple Kubernetes clusters and core datastores (PostgreSQL, Gitaly, Redis, Elasticsearch) running outside Kubernetes. Secret management uses Google KMS for GCP services and Chef Encrypted Data Bags for other host secrets.
DevTools
Now part of IBM; HashiCorp Cloud Platform (HCP) for Terraform/Vault/Consul runs on AWS. Core tools are widely-adopted open-source (BSL-licensed) infra-as-code and secrets management.