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Azure App Configuration is a service that centralizes application settings and feature flags. It helps developers separate configuration from their application code, which is especially useful for microservices and serverless apps that run in many places. This prevents errors and makes managing settings easier.
To keep data safe, App Configuration uses encryption at rest and in transit. The most secure way for applications to access these settings is by using managed identities, which allow Azure services to authenticate without storing passwords or connection strings. When sensitive secrets like API keys are needed, they should be stored in Azure Key Vault, and App Configuration can point to them using Key Vault references.
The service also includes tools for feature management, letting you turn features on or off in real time without restarting your app. To make applications more efficient, you can use a sentinel key; the app only checks for updates when this specific key changes, reducing the number of calls to Azure. For high availability, App Configuration supports geo-replication and availability zones, and features like Configuration Snapshots and Customer-Managed Keys help keep deployments safe and under your control.
Azure Key Vault is a secure place to store sensitive information like passwords, API keys, and certificates. Using it prevents secrets from being hardcoded into your application, which reduces the risk of them being exposed. Key Vault encrypts all secrets and tracks changes with versioning, so you can see a history or roll back if needed.
Access to the vault is controlled through role-based access control (RBAC) and access policies. You assign roles like Key Vault Secrets User to grant specific permissions, following the principle of least privilege so identities only get the access they absolutely need. Applications can connect to Key Vault using managed identities, client secrets, or certificates, with managed identities being the most secure as they handle credentials automatically.
Applications retrieve secrets by creating Key Vault references in their code or in App Configuration. The application's code uses a SecretClient and a credential like DefaultAzureCredential to authenticate and fetch the secret value. To keep applications secure, you should implement secret rotation to regularly update secrets and set up refresh intervals so apps automatically get the latest values without a restart.
Azure App Configuration and Azure Key Vault are designed to work together. App Configuration manages general settings and feature flags, while Key Vault stores the actual secrets. They connect using Key Vault references, which are pointers stored in App Configuration that tell your app where to find a secret in Key Vault. This keeps sensitive data locked in the vault while your app still gets a unified configuration experience.
The most secure way for your application to access both services is by using managed identities. When your app runs on Azure services like App Service or Azure Functions, you can enable a managed identity and grant it the App Configuration Data Reader role and the necessary permissions in Key Vault. This removes the need to manage any passwords or connection strings in your code.
For best performance and security, use role-based access control (RBAC) to enforce strict permissions. Configure your app to refresh its configuration at set intervals, watching a sentinel key to know when to check for updates. This allows for dynamic changes, like toggling feature flags, without restarting the application. Always include error handling so your app can stay stable if the configuration services are temporarily unavailable.
Azure App Configuration provides a single, central place to store all your application's settings and feature flags. This is crucial for modern applications like microservices, as it prevents configuration errors and makes deployments smoother. You organize settings using key prefixes for grouping and labels to have different values for the same key in environments like development, staging, and production.
Feature flags let you control the availability of features in your application dynamically. You can turn features on or off, or roll them out gradually to specific users, all without needing to redeploy your code. The service includes a dedicated interface for managing these flags, and your app can be set to refresh its configuration by watching for changes to a single sentinel key.
For security, always pair App Configuration with Azure Key Vault for storing secrets. Use managed identities for authentication instead of connection strings, and assign the App Configuration Data Reader role to your application's identity. To ensure high availability, deploy your App Configuration store in regions that support availability zones and enable geo-replication. Tools like configuration snapshots let you test settings safely before promoting them to production.
Azure App Configuration and Azure Key Vault form a complete system for managing application settings. App Configuration handles non-sensitive settings and feature flags, while Key Vault is the secure, dedicated vault for secrets like connection strings and API keys. Keeping configuration separate from code and storing secrets in a specialized vault is a foundational security best practice.
The recommended way for applications to authenticate to these services is by using Managed Identities. These are automatically managed identities within Microsoft Entra ID. A system-assigned identity is created for a single Azure resource, while a user-assigned identity can be shared across multiple resources. Using managed identities means your application code never contains or manages passwords, drastically improving security.
Access to secrets in Key Vault is controlled through Azure Role-Based Access Control (RBAC) or vault access policies. RBAC is preferred because it allows you to grant very specific permissions (like "read a secret") at different scopes (like an entire subscription or just one vault). Applying the principle of least privilege ensures each identity has only the minimum permissions it needs to function.
Secret rotation is the process of regularly updating secrets to limit damage if they are ever leaked. Key Vault supports automatic rotation for many types of secrets. When applications use Key Vault references (for example, in App Service), the platform automatically retrieves the latest secret version, typically refreshing the cached value within 24 hours.
A complete security strategy includes monitoring and logging all access to secrets. Services like Azure Monitor and Azure Event Grid provide audit trails showing who accessed what secret and when. For added protection, you can use network isolation techniques like firewalls and private endpoints to restrict vault access to only trusted applications within a specific virtual network.
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