• Azure cosmos DB supports managed identity access at system level as well as user-based level. Thus, you can configure managed identity access to azure cosmos DB through a spring boot application hosted in azure AKS cluster by configuring the managed identity for the configured spring boot app as below: -

Go to your cosmos DB account  Settings  Identity  System assigned, or User assigned  Save. You can also set azure active directory-based role assignments to the cosmos DB account as well.

• If you access your hosted spring boot app in AKS and retrieve the service principal ID for assigning a system managed identity through role assignment to azure cosmos DB for managed identity access, you can run use the following command for assigning the service principal to a parameter, then assign a response, content and ARMToken parameter and then use the access token retrieved earlier to get the access keys to access the cosmos DB.

Note : - Below is a sample command to assign a service principal to a parameter

 ‘ $spID = (Get-AzVM -ResourceGroupName myRG -Name 
  myVM).identity.principalid
  New-AzRoleAssignment -ObjectId $spID -RoleDefinitionName 
  "Cosmos DB Account Reader Role" -Scope 
  "/subscriptions/<mySubscriptionID>/resourceGroups/
  <myResourceGroup>/providers/
   Microsoft.DocumentDb/databaseAccounts/<COSMOS DB ACCOUNT 
   NAME>" '

Please find the below links for more information: -

https://docs.microsoft.com/en-us/azure/active-directory/managed-identities-azure-resources/tutorial-windows-vm-access-cosmos-db

https://docs.microsoft.com/en-us/azure/cosmos-db/managed-identity-based-authentication