Explanation
Adding Request Policies and Response Policies to API Deployment Specifications:
You can control thebehavior of an API deployment you create on an API gateway by adding request and response policies to the API deployment specification:
a request policy describes actions to be performed on an incoming request from a caller before it is sent to a back end a response policy describes actions to be performed on a response returned from a back end before it is sent to a caller You can use request policies to:
limit the number of requests sent to back-end services
enable CORS (Cross-Origin Resource Sharing) support
provide authentication and authorization
You can add request and response policies that apply globally to all routes in an API deployment specification, and also (in some cases) request and response policies that apply only to particular routes.
Notethe following:
No response policies are currently available.
API Gateway request policies and response policies are different to IAM policies, which control access to Oracle Cloud Infrastructure resources.
You can add request and response policies to anAPI deployment specification by:
using the Console
editing a JSON file
References:
https://docs.cloud.oracle.com/en-us/iaas/Content/APIGateway/Tasks/apigatewayaddingrequestpolicies.htm

Explanation
You can invoke a function that you've deployed to Oracle Functions in different ways:
Using the Fn Project CLI.
Using the Oracle Cloud Infrastructure CLI.
Using the Oracle Cloud Infrastructure SDKs.
Making a signed HTTP request to the function's invoke endpoint. Every function has an invoke endpoint.
Each of the above invokes the function via requests to the API. Any request to the API must be authenticated by including a signature and the OCID of the compartmentto which the function belongs in the request header.
Such a request is referred to as a 'signed' request. The signature includes Oracle Cloud Infrastructure credentials in an encrypted form.

Explanation
Before using Oracle Functions, you must have an Oracle Cloud Infrastructure CLI configuration file that contains the credentials of the user accountthat you will be using to create and deploy functions. These user account credentials are referred to as a 'profile'.
By default, the Oracle Cloud Infrastructure CLI configuration file is located at ~/.oci/config. You might already have a configuration file as a result of installing the Oracle Cloud Infrastructure CLI. However, you don't need to have installed the Oracle Cloud Infrastructure CLI in order to use Oracle Functions.
References:
https://docs.cloud.oracle.com/en-us/iaas/Content/Functions/Tasks/functionsconfigureocicli.htm#:~:text=By%20d
https://docs.cloud.oracle.com/en-us/iaas/Content/API/SDKDocs/cliconfigure.htm

Explanation
What is a Pod Security Policy?
A Pod Security Policy is a cluster-level resource that controlssecurity sensitive aspects of the pod specification. The PodSecurityPolicy objects define a set of conditions that a pod must run with inorder to be accepted into the system, as well as defaults for the related fields. They allow an administrator to control the following:
Privilege Escalation
These options control the allowPrivilegeEscalation container option. This bool directly controls whether the no_new_privs flag gets set on the container process. This flag will prevent setuid binaries from changing the effective user ID, and prevent files from enabling extra capabilities (e.g. it will prevent the use of the ping tool). This behavior is required to effectively enforce MustRunAsNonRoot.
example:
# Require the container to run without root privileges.
rule: 'MustRunAsNonRoot'

Explanation
Service Aggregator Pattern
Another option for eliminating microservice-to-microservice coupling is an Aggregator microservice, shown in purple in Figure 4-10.

The pattern isolates an operation that makes calls to multiple back-end microservices, centralizing its logic into a specialized microservice.The purple checkout aggregator microservice in the previous figure orchestrates the workflow for the Checkout operation. It includes calls to several back-end microservices in a sequenced order. Data from the workflow is aggregated and returned to the caller. While it still implements direct HTTP calls, the aggregator microservice reduces direct dependencies among back-end microservices.
References:
https://docs.microsoft.com/en-us/dotnet/architecture/cloud-native/service-to-service-communication#:~:text=Ser