Rule of thumb:

• Secrets → Key Vault
• Configs → App Configuration
• Use both for secure + flexible configuration management.

Azure Key Vault

Purpose: Securely store sensitive information such as secrets, keys, and certificates.

• Use Cases:

  • Store API keys, connection strings, tokens.
  • Manage and rotate TLS/SSL certificates.
  • Protect cryptographic keys used for encryption/decryption.

• Strengths:

  • Built-in hardware security module (HSM) support.
  • Access policies and RBAC for fine-grained control.
  • Automatic secret rotation with some Azure services.
  • Logging and monitoring via Azure Monitor.

• Limitations:

  • Not designed for feature flags or configuration settings that change frequently.
  • API calls can add latency if used excessively at runtime.

Azure App Configuration

Purpose: Centralized application configuration management.

• Use Cases:

  • Store non-sensitive app settings (feature flags, UI options, app behavior).
  • Versioned configurations and labels (per environment, per region).
  • Enable dynamic configuration refresh in apps.

• Strengths:

  • Feature flag management built-in.
  • Supports key-value pairs with labels for environment separation.
  • Integration with Azure Functions, App Service, AKS, and more.
  • High availability and global distribution.

• Limitations:

  • Not designed to store secrets or keys.
  • Does not provide encryption key lifecycle management.

When to Use Which

• Use Key Vault when:

  • Handling secrets (DB passwords, API keys).
  • Managing certificates and encryption keys.
  • Need secure storage with strong access policies.

• Use App Configuration when:

  • Handling app configs (feature flags, toggle dark mode, regional endpoints).
  • Need dynamic refresh without redeployment.
  • Want environment-based configuration with versioning.

How They Work Together

In most real-world solutions, you combine both:

• Use Azure App Configuration for general settings and feature management.
• Reference Azure Key Vault inside App Configuration for sensitive values.

• Example:

  • AppConfig:DbConnectionString → points to Key Vault secret.
  • App reads all configs from App Configuration → securely resolves secrets from Key Vault when needed.