Manage Azure App Configuration with TypeScript

Azure App Configuration SDK for TypeScript is a client for centralized configuration management with feature flags and dynamic refresh. It ships as three separate packages: a low-level CRUD SDK for directly managing settings, a high-level provider recommended for applications loading runtime configuration, and a feature-flag management package. It authenticates via DefaultAzureCredential or a connection string.

The low-level SDK covers full CRUD: addConfigurationSetting (fails if the key already exists) versus setConfigurationSetting (create-or-update, with optimistic concurrency via onlyIfUnchanged), reading a single setting or listing settings filtered by key and label, deleting a setting, and locking/unlocking a setting as read-only. The high-level provider's load() function pulls in settings by key/label selectors, can trim key prefixes, and exposes both map-style (.get()) and object-style (constructConfigurationObject) access. Dynamic refresh is configured with a refresh interval, triggered manually or via an onRefresh() listener - a common pattern calls refresh() inside request middleware so config picks up changes without redeploying. Key Vault references resolve automatically: configuring keyVaultOptions with a refresh interval means a value like a database password is transparently pulled from Key Vault when read.

Feature flags follow the standard Azure App Configuration schema - a flag has an enabled state and conditions.clientFilters, such as Microsoft.Targeting with named users, named groups at a rollout percentage, and a default rollout percentage for everyone else. Loading feature flags through the provider and evaluating them with FeatureManager.isEnabled() supports both a simple boolean check and a targeting-context check (a user ID and group list). Snapshots let you freeze a filtered set of settings under a name with a retention period, then load configuration from that snapshot instead of live settings - useful for pinning a release's configuration; snapshots can also be archived and recovered. Labels are the mechanism for separating configuration by environment (the same key can hold different values under a "development" and a "production" label, and settings can be listed with no label at all via a null-byte label filter).

Use it when you need centralized, dynamically-refreshable configuration and feature flags shared across services or environments, rather than static per-deployment config files. Use the provider package for runtime configuration loading in an app, and reserve the low-level CRUD SDK for management/automation tasks (seeding, migrating, or auditing settings) - mixing the two roles in application code is exactly what the skill's own best practices warn against.

Input is configuration keys, values, labels, and feature-flag definitions, plus the App Configuration endpoint or connection string. Output is resolved configuration values (including auto-resolved Key Vault secrets) and feature-flag evaluation results, refreshed on an interval or on demand. Install the packages you need:

### Low-level CRUD SDK
npm install @azure/app-configuration @azure/identity

### High-level provider (recommended for apps)
npm install @azure/app-configuration-provider @azure/identity

### Feature flag management
npm install @microsoft/feature-management

It combines @azure/app-configuration (CRUD), @azure/app-configuration-provider (runtime loading with refresh and Key Vault resolution), @microsoft/feature-management (feature-flag evaluation), and @azure/identity for authentication, with RBAC access controlled via roles like App Configuration Data Reader.

TypeScript/Node developers building apps that need centralized, environment-labeled configuration with a tuned refresh cadence (config refreshed on a 30-second interval, Key Vault secrets on a 2-hour interval), and feature-flag targeting/rollout rather than hardcoded config files.