Yes, Ory Oathkeeper can be replaced with other API gateways like Kong or Nginx when self-hosting Kratos. Ory Oathkeeper is used as a Policy Enforcement Point (PEP) in your cloud architecture, acting as a reverse proxy in front of your upstream API or web server. However, if you want to use another API Gateway like Kong or Nginx, Oathkeeper can plug into that and act as its Policy Decision Point (PDP) [source](https://www.ory.sh/docs/oathkeeper). For example, Ory Kratos can work very well with reverse proxies such as Nginx, Envoy, or Kong to route and authorize traffic to applications [source](https://www.ory.sh/docs/kratos/guides/zero-trust-iap-proxy-identity-access-proxy). If you choose to use Nginx, there are guides available on how to install and configure Nginx as a reverse proxy and load balancer for your service [source](https://www.ory.sh/docs/kratos/guides/deploy-kratos-example#install-and-configure-nginx). However, please note that while you can replace Oathkeeper with other API gateways, Oathkeeper provides specific features such as the Access Control Decision API that works with various services [source](https://www.ory.sh/docs/oathkeeper). If you need these features, you might need to implement them separately when using other API gateways.