Core Concepts

This page covers the foundational architecture and design decisions behind AppDNA. Understanding these concepts will help you integrate the SDK effectively and get the most out of the platform.

SDK Architecture

The AppDNA SDK follows a singleton pattern with module namespaces. After calling configure(), the SDK is accessible through a single global instance. Each feature area is organized as a namespace on that instance:

Namespace	Purpose
`push`	Push notification registration and handling
`billing`	Subscription status, product fetching, purchases
`onboarding`	Server-driven onboarding flow presentation
`paywall`	Server-driven paywall rendering and events
`remoteConfig`	Key-value remote configuration
`features`	Feature flags and entitlements
`experiments`	A/B experiment assignment and exposure tracking
`surveys`	In-app survey presentation and response collection
`inAppMessages`	Triggered in-app messaging
`deepLinks`	Deep link routing and deferred deep links

Each namespace operates independently but shares the core event pipeline, identity state, and configuration layer.

iOS
Android
Flutter
React Native

// Access module namespaces
AppDNA.push.requestPermission()
AppDNA.billing.getProducts()
AppDNA.experiments.getVariant("onboarding-v2")
AppDNA.remoteConfig.getString("welcome_message")

// Access module namespaces
AppDNA.push.requestPermission()
AppDNA.billing.getProducts()
AppDNA.experiments.getVariant("onboarding-v2")
AppDNA.remoteConfig.getString("welcome_message")

// Access module namespaces
await AppDNA.push.requestPermission();
await AppDNA.billing.getProducts();
AppDNA.experiments.getVariant("onboarding-v2");
AppDNA.remoteConfig.getString("welcome_message");

// Access module namespaces
await AppDNA.push.requestPermission();
await AppDNA.billing.getProducts();
AppDNA.experiments.getVariant("onboarding-v2");
AppDNA.remoteConfig.getString("welcome_message");

Offline-First Design

AppDNA SDKs are built for unreliable networks. The SDK never assumes connectivity is available and degrades gracefully when it is not.

Configuration Priority

The SDK resolves configuration using a three-tier fallback:

Remote (Firestore real-time sync)
        │
        ▼ unavailable?
Cached (persisted on device from last successful fetch)
        │
        ▼ unavailable?
Bundled (appdna-config.json embedded in the app binary)

Source	Description	Latency
Remote	Real-time sync from Firestore. Always preferred when available.	~100ms
Cached	Last known good config, persisted in local storage. Expires after the configured TTL.	~1ms
Bundled	Static JSON file shipped with the app binary. Used on first launch before any network call completes.	~1ms

The default config TTL is 5 minutes. After the TTL expires, the SDK attempts a remote fetch. If the fetch fails, the cached config continues to be used until a successful refresh.

Event Queue

Events are never dropped. When the SDK records an event:

The event is written to a persistent on-disk queue (Keychain on iOS, SharedPreferences on Android).
The queue is auto-flushed every 30 seconds or when it reaches 20 events, whichever comes first.
If the flush fails (no connectivity, server error), events remain in the queue and are retried on the next flush cycle.
Events are only removed from the queue after a successful server acknowledgment.

Because events are persisted to disk, they survive app restarts and even device reboots. No event is ever lost due to a crash or force-quit.

Config Bundle

A config bundle is a versioned JSON snapshot generated server-side. It contains all active configuration for your app: onboarding flows, paywalls, in-app messages, experiments, feature flags, and remote config values.

How It Works

The dashboard generates a new bundle version whenever you publish a change.
The SDK polls GET /api/v1/sdk/config-bundle/version to check for updates.
If a newer version exists, the SDK downloads the full bundle and caches it locally.
The bundle can also be embedded in your app binary for zero-latency first launch.

Embedding a Bundle

For the best first-launch experience, embed the latest config bundle in your app:

iOS
Android
Flutter
React Native

Add appdna-config.json to your Xcode project as a bundle resource.

Place appdna-config.json in the assets/ directory.

Add appdna-config.json to your assets/ folder and declare it in pubspec.yaml.

Place appdna-config.json in your project root or assets directory.

The embedded bundle is a fallback only. The SDK will always prefer a fresher remote or cached config when available. Embedding a bundle ensures your app works correctly on first launch before any network request completes.

Experiments

AppDNA experiments use deterministic bucketing to assign users to variants. No server call is required — the assignment is computed locally on the device.

How Bucketing Works

The SDK computes a bucket using:

bucket = MurmurHash3(userId + experimentId + salt) % 100

Input	Source
`userId`	The identified user ID (or anonymous ID if not identified)
`experimentId`	Unique identifier for the experiment
`salt`	Random string generated when the experiment is created

The resulting bucket (0–99) maps to a variant based on the traffic allocation configured in the dashboard.

Key Properties

Deterministic: The same user always gets the same variant for the same experiment. No randomness, no server dependency.
Cross-platform consistent: A user who opens your app on iOS and Android will see the same variant because the hash function and inputs are identical.
Session-stable: The variant does not change between sessions or app restarts.
Exposure tracking: The SDK records an exposure event once per session when getVariant() is called. This prevents inflated exposure counts from multiple reads.

iOS
Android
Flutter
React Native

let variant = AppDNA.experiments.getVariant("onboarding-v2")

switch variant {
case "control":
    showClassicOnboarding()
case "streamlined":
    showStreamlinedOnboarding()
default:
    showClassicOnboarding()
}

val variant = AppDNA.experiments.getVariant("onboarding-v2")

when (variant) {
    "control" -> showClassicOnboarding()
    "streamlined" -> showStreamlinedOnboarding()
    else -> showClassicOnboarding()
}

final variant = AppDNA.experiments.getVariant("onboarding-v2");

if (variant == "streamlined") {
  showStreamlinedOnboarding();
} else {
  showClassicOnboarding();
}

const variant = AppDNA.experiments.getVariant("onboarding-v2");

if (variant === "streamlined") {
  showStreamlinedOnboarding();
} else {
  showClassicOnboarding();
}

Delegates and Callbacks

All SDK modules use a delegate/callback pattern to communicate events back to your application. This keeps the SDK non-blocking and lets you respond to events in your own code.

iOS
Android
Flutter
React Native

Modules expose protocols with default empty implementations. Conform to only the methods you need:

class MyPaywallHandler: PaywallDelegate {
    func paywallDidPresent(paywallId: String) {
        // Track in your own analytics
    }

    func paywallDidDismiss(paywallId: String, action: PaywallAction) {
        // Handle purchase or dismissal
    }
}

AppDNA.paywall.delegate = MyPaywallHandler()

Modules expose interfaces with default methods. Override only what you need:

AppDNA.paywall.delegate = object : PaywallDelegate {
    override fun onPaywallPresented(paywallId: String) {
        // Track in your own analytics
    }

    override fun onPaywallDismissed(paywallId: String, action: PaywallAction) {
        // Handle purchase or dismissal
    }
}

Modules use abstract classes that you extend:

class MyPaywallHandler extends PaywallDelegate {
  @override
  void onPaywallPresented(String paywallId) {
    // Track in your own analytics
  }

  @override
  void onPaywallDismissed(String paywallId, PaywallAction action) {
    // Handle purchase or dismissal
  }
}

AppDNA.paywall.delegate = MyPaywallHandler();

Modules use event emitter listeners with unsubscribe functions:

const unsubscribePresented = AppDNA.paywall.onPresented((paywallId) => {
  // Track in your own analytics
});

const unsubscribeDismissed = AppDNA.paywall.onDismissed((paywallId, action) => {
  // Handle purchase or dismissal
});

// Clean up when no longer needed
unsubscribePresented();
unsubscribeDismissed();

Environments

AppDNA supports two environments to separate development and production data:

Environment	API Base URL	Key Prefix
Production	`https://api.appdna.ai`	`adn_live_`
Sandbox	`https://sandbox-api.appdna.ai`	`adn_test_`

Events, experiments, and configuration are completely isolated between environments.
Use sandbox during development and testing. Switch to production for App Store / Play Store builds.
The SDK determines the environment from the API key prefix — there is no need to set it separately if the key is correct.

Never ship an app to production with a sandbox API key. Sandbox data is periodically purged and is not included in production analytics.

Webhooks

AppDNA can send real-time HTTP callbacks to your server whenever key events occur. Webhooks let you sync data to your backend, trigger workflows, or feed events into third-party tools.

Event Types

AppDNA supports 16 webhook event types spanning the full lifecycle:

Category	Events
User	`user.created`, `user.identified`, `user.trait_updated`
Subscription	`subscription.started`, `subscription.renewed`, `subscription.cancelled`, `subscription.expired`
Experiment	`experiment.exposure`, `experiment.conversion`
Paywall	`paywall.presented`, `paywall.dismissed`, `paywall.purchase_started`, `paywall.purchase_completed`
Push	`push.delivered`, `push.opened`
Onboarding	`onboarding.completed`

Security

Every webhook payload is signed with HMAC-SHA256. Your server should verify the signature before processing:

X-AppDNA-Signature: sha256=<hex-encoded HMAC of request body>

The signing secret is generated when you create a webhook endpoint in the dashboard and is only displayed once.

Reliability

5 retry attempts with exponential backoff (1s, 5s, 30s, 2min, 10min).
Your endpoint must respond with a 2xx status within 15 seconds or the attempt is considered failed.
After 50 consecutive failures, the webhook endpoint is automatically disabled and you receive an email notification.
You can view delivery logs and manually retry failed deliveries in the dashboard.

To test webhooks locally during development, use a tunneling tool like ngrok and point your webhook endpoint to the tunnel URL.

Identity

AppDNA manages user identity through a combination of anonymous and authenticated identifiers.

Anonymous ID

On first launch, the SDK generates a random anonymous ID and persists it securely:

Platform	Storage
iOS	Keychain
Android	SharedPreferences (encrypted)
Flutter	Platform-specific (Keychain on iOS, SharedPreferences on Android)
React Native	Platform-specific (Keychain on iOS, SharedPreferences on Android)

The anonymous ID survives app restarts and reinstalls (on iOS, as long as the Keychain entry is preserved).

Linking Identity

When you call identify(userId:), the SDK links the anonymous ID to the provided user ID. All past events tracked under the anonymous ID are retroactively associated with the user.

Anonymous ID (auto-generated)  ──identify()──▶  User ID (your system)

Resetting Identity

Calling reset() clears the user ID but keeps the anonymous ID. This is appropriate for sign-out flows where another user may sign in on the same device.

iOS
Android
Flutter
React Native

// User signs out
AppDNA.reset()

// New user signs in
AppDNA.identify(userId: "user-456", traits: ["plan": "free"])

// User signs out
AppDNA.reset()

// New user signs in
AppDNA.identify(userId = "user-456", traits = mapOf("plan" to "free"))

// User signs out
await AppDNA.reset();

// New user signs in
await AppDNA.identify("user-456", traits: {"plan": "free"});

// User signs out
await AppDNA.reset();

// New user signs in
await AppDNA.identify("user-456", { plan: "free" });

The anonymous ID is never deleted by reset(). This ensures continuity for device-level analytics even across multiple user sessions.

Getting Started

​Core Concepts

​SDK Architecture

​Offline-First Design

​Configuration Priority

​Event Queue

​Config Bundle

​How It Works

​Embedding a Bundle

​Experiments

​How Bucketing Works

​Key Properties

​Delegates and Callbacks

​Environments

​Webhooks

​Event Types

​Security

​Reliability

​Identity

​Anonymous ID

​Linking Identity

​Resetting Identity

Core Concepts

SDK Architecture

Offline-First Design

Configuration Priority

Event Queue

Config Bundle

How It Works

Embedding a Bundle

Experiments

How Bucketing Works

Key Properties

Delegates and Callbacks

Environments

Webhooks

Event Types

Security

Reliability

Identity

Anonymous ID

Linking Identity

Resetting Identity