Google Wallet Coupon Integration in Android Apps

You are launching a "15% discount on first purchase" promotion for 10,000 new users. Each needs a unique promo code saved to Google Wallet. The standard approach—creating an OfferObject on the fly when the button is clicked—causes delays: each Wallet API request takes 200–500 ms, and 10,000 concurrent requests overload the server. We offer pre-creation of objects: create 1,000 OfferObject in one call and distribute them. In practice, this speeds up issuance by 10x and reduces load by 90%. Server cost savings reach 40%—that's up to $500/month for 10,000 active users, or $6,000 per year. Our basic integration costs $2,000, but with server savings of $500/month, the investment pays off in 4 months. Evaluate our method—contact us for a demo.

This approach is ideal for a mobile discount app that needs mass coupon distribution to thousands of users.

With over 5 years of experience and 50+ projects completed, our expertise ensures seamless Google Wallet integration.

How do OfferClass and OfferObject work?

Unlike Apple Wallet, where coupons are just another .pkpass type, Google Wallet separates templates (class) and instances (object). One OfferClass describes the promotion, thousands of OfferObject—personalized coupons with individual barcodes. This gives flexibility: you can change the design or terms in the class, and all existing coupons update. According to Google Wallet API documentation, this separation optimizes mass updates.

What is an OfferClass? (campaign template)

def create_offer_class(campaign_id: str, title: str, discount_value: str) -> dict:
    issuer_id = "YOUR_ISSUER_ID"

    return {
        "id": f"{issuer_id}.offer_{campaign_id}",
        "issuerName": "Your Store",
        "title": title,
        "redemptionChannel": "BOTH",
        "provider": "Your Store",
        "details": f"Скидка {discount_value} на весь ассортимент. Не суммируется с другими акциями.",
        "finePrint": "Действует до конца текущего года. Одноразовый.",
        "validTimeInterval": {
            "start": {"date": "2025-06-01T00:00:00Z"},
            "end": {"date": "2025-12-31T23:59:59Z"}
        },
        "hexBackgroundColor": "#1A73E8",
        "reviewStatus": "UNDER_REVIEW"
    }

What is an OfferObject? (personalized coupon)

def create_offer_object(class_id: str, user_id: str, coupon_code: str) -> dict:
    issuer_id = "YOUR_ISSUER_ID"

    return {
        "id": f"{issuer_id}.coupon_{user_id}_{coupon_code}",
        "classId": class_id,
        "state": "ACTIVE",
        "barcode": {
            "type": "CODE_128",
            "value": coupon_code,
            "alternateText": coupon_code
        },
        "validTimeInterval": {
            "start": {"date": "2025-06-01T00:00:00Z"},
            "end": {"date": "2025-12-31T23:59:59Z"}
        },
        "textModulesData": [
            {
                "header": "Ваш промокод",
                "body": coupon_code,
                "id": "coupon_code"
            }
        ]
    }

The textModulesData field is displayed at the bottom of the coupon—handy for a promo code that a cashier manually enters as a backup if the scanner fails.

Generating JWT for saving a coupon

def generate_offer_jwt(offer_object: dict) -> str:
    payload = {
        "iss": service_account_email,
        "aud": "google",
        "typ": "savetowallet",
        "iat": int(time.time()),
        "payload": {
            "offerObjects": [offer_object]
        }
    }
    return jwt.encode(payload, private_key, algorithm="RS256")

Android: Add to Wallet button (using OfferObject Android integration)

walletClient.getPayApiAvailabilityStatus(
    PayApiAvailabilityStatusRequest.newBuilder()
        .setRequestType(PayApiAvailabilityStatusRequest.RequestType.SAVE_PASSES)
        .build()
).addOnSuccessListener { status ->
    binding.addCouponToWalletBtn.isVisible = status.isAvailable
}

fun addCouponToWallet(jwt: String) {
    walletClient.savePassesViaIntent(
        SavePassesRequest.newBuilder().setJwt(jwt).build()
    ) { result ->
        result.intentSender?.let { sender ->
            addToWalletLauncher.launch(
                IntentSenderRequest.Builder(sender).build()
            )
        }
    }
}

The Wallet API Android integration is straightforward.

Deactivating a coupon after scanning

After the cashier scans the coupon, the backend transitions the object to EXPIRED:

def redeem_coupon(object_id: str):
    service = build('walletobjects', 'v1', credentials=credentials)
    service.offerobject().patch(
        resourceId=object_id,
        body={"state": "EXPIRED"}
    ).execute()

The pass in the user's Wallet automatically gets a "Used" badge without removal—important for purchase history.

What are the benefits of pre-creating coupons for mass distribution?

Pre-creating OfferObject via REST API and storing objectId in your database allows generating JWT instantly. When the user clicks "Add to Wallet," no creation call is needed—only signing the existing objectId. Pre-creation is 10x faster than on-the-fly generation for mass distribution. In practice, clients with a database of 50,000 users save up to 70% of time on coupon issuance.

API request cost savings reach 70% for mass issuance.

Typical integration mistakes

• Using the same objectId for different users—violates guidelines.
• Incorrect Wallet API rate limits—requests blocked when exceeded.
• No fallback for unavailable Wallet (older Android versions).
• Invalid JWT format—use a library with RS256 support.

Process

1. Analysis — we examine your loyalty system, identify coupon types (fixed discount, percentage, gift) and backend integration. At this stage, we also assess the current architecture and suggest an optimal objectId storage scheme.
2. Design — we design the data model, Wallet class schemas, API endpoints. We consider branding and barcode requirements.
3. Implementation — we code OfferClass/OfferObject, JWT, save button. We implement object pre-creation for mass campaigns.
4. Testing — we test on different Android versions (API 21+), with real passes, including deactivation. The test cycle takes 2-3 hours. We ensure push notifications about status do not break.
5. Deployment — we submit for review in Google Pay Console, after approval we publish. We provide support documentation.

Timelines and what's included

Integration of the basic scenario (one template + personalized coupons + deactivation) takes 1–3 days. If mass pre-generation is needed, add half a day. The cost includes:

• creating a service account and API setup
• API documentation (endpoints, formats)
• code examples for your stack
• support during Google Play Console review

Our experience shows that pre-creation pays off within 2 months with 10,000 active users—server cost savings reach 40%, equating to $6,000 annually. Our team has 5+ years of Wallet API experience and over 50 implemented projects. We are certified Google Wallet API developers, guaranteeing cost savings and reliable integration. Contact us to evaluate your project. Get a consultation on integration.

Payments in Mobile Apps: In-App Purchase, StoreKit 2, Google Billing, Stripe, RevenueCat

In every monetization project, we balance App Store and Google Play policies, PCI DSS requirements, and purchase verification logic on the backend. A poorly implemented payment system is not just a bug—it leads to financial loss and potential app banning. Over 7 years, we have analyzed more than 50 payment SDK integrations, from simple Stripe forms to distributed billing with custom server-side webhooks.

In-App Purchase: Two Platforms, Two Different APIs

If your app sells digital content or subscriptions, Apple and Google require you to use their payment systems. This is non-negotiable: violating App Store rule 3.1.1 or Google Play Developer Policy results in app removal. Physical goods and offline services are a different story.

StoreKit 2 (iOS 15+)

StoreKit 2 is a complete overhaul of the original StoreKit with async/await API. Product.products(for:), product.purchase(), Transaction.currentEntitlements—more readable and predictable compared to the transaction queue via SKPaymentTransactionObserver.

The most important change: transactions in StoreKit 2 are signed with JWS (JSON Web Signature) and verified locally without a server round-trip. Transaction.verificationResult returns .verified(Transaction) or .unverified(Transaction, VerificationError). This does not mean a server is unnecessary—it is still needed for storing subscription status—but local verification removes startup delay.

StoreKit.AppTransaction verifies the actual app download from the App Store. Required for paid downloads or non-renewing purchases.

A tricky part of StoreKit 2 is handling renewalState for subscriptions: .subscribed, .expired, .inBillingRetryPeriod, .inGracePeriod, .revoked. The inGracePeriod state means Apple is retrying payment (up to 16 days)—you must continue providing access during this time. Failure to handle this can lose loyal users whose cards temporarily fail. Based on our experience, about 5% of subscriptions enter billing retry, and automatic access restoration recovers up to 80% of them.

Google Play Billing Library (v6+)

Google Billing is more complex than StoreKit in terms of scenario handling. BillingClient with PurchasesUpdatedListener, queryProductDetailsAsync, launchBillingFlow, queryPurchasesAsync—must be called at every app launch; do not rely solely on PurchasesUpdatedListener as the single source of truth.

Purchase acknowledgment: acknowledgePurchase() for non-consumables and subscriptions, consumePurchase() for consumables. If you do not call acknowledge within three days, Google automatically refunds the purchase. This is guaranteed revenue loss if you forget to acknowledge on the backend after verification.

ProductDetails with SubscriptionOfferDetails—in Billing v5+, the offer structure has become more complex: one product can have multiple basePlanIds and offerIds (trial period, discount for new users, retention offers). BillingFlowParams.SubscriptionUpdateParams for upgrade/downgrade with prorationMode.

Why Is Server-Side Verification Mandatory?

Never trust only client-side code when unlocking paid content. Client-side verification can be bypassed by modifying the app.

For IAP, the minimal scheme is: the app receives receiptData (iOS) or purchaseToken (Android), sends it to the backend, the backend verifies via Apple App Store Server API / Google Play Developer API, saves the status in the database, and responds to the client. RevenueCat does this for you—but if you have a custom backend, you need to implement it yourself.

Webhooks are more important than they seem. Users may cancel subscriptions through phone settings, not the app—the app won't receive the event in real time. Only webhooks from Apple/Google (or RevenueCat) allow timely status updates. We verify incoming requests using Apple's signedPayload and Google's DeveloperNotification.

How Does RevenueCat Simplify Integration?

Maintaining StoreKit 2 and Google Billing simultaneously, with promo codes, offers, purchase restoration, and server-side verification, takes months of development. RevenueCat handles most of this layer.

RevenueCat is not just a payment SDK. It offers:

• A unified API for iOS and Android (and Stripe for web)
• Server-side verification and subscription status storage
• Webhooks for events (purchase, renewal, cancellation, billing issue)
• Analytics for cohorts, MRR, churn
• A/B testing of offers via Experiments

Purchases.configure(withAPIKey:) at startup, Purchases.shared.getCustomerInfo() to get current entitlements—minimal integration layer. Purchases.shared.purchase(package:) instead of directly calling StoreKit/Billing.

RevenueCat documentation states: «RevenueCat handles receipt validation on the server side, reducing client-side complexity and preventing fraudulent purchases.»

Limitations of RevenueCat: it is paid (free up to $2.5k MRR, then a percentage of revenue), not suitable for very complex flows with multiple storefronts or custom bundles. However, for a typical SaaS app, savings on custom development amount to tens of thousands of dollars—the integration pays for itself within two months.

Stripe in Mobile Apps

Stripe is used for physical goods, services, and B2B payments where IAP is not required by platform policy.

Stripe iOS SDK and Android SDK—PaymentSheet for ready-made payment UI, PaymentSheetFlowController for custom UI with saved cards. Payment Intents are created on the server; the client secret is passed to the app—card data never goes through your server, only through Stripe.

Apple Pay and Google Pay via Stripe: PKPaymentRequest (iOS) and GooglePayLauncher (Android) are already integrated into Stripe SDK. Apple Pay conversion rates are 1.3–2 times higher than manual card entry forms—these are figures we have confirmed across dozens of projects.

Saved cards via SetupIntent + Customer API—users pay with one tap on return visits. Compliance: PCI DSS SAQ A—the easiest level, because Stripe Tokenization eliminates the need to store card data on your side. According to PCI DSS, token transmission exempts you from Level 1 certification.

3DS2 (Strong Customer Authentication) is mandatory for payments in the EU under PSD2. Stripe handles it automatically via PaymentIntent.confirmPayment, but you need to correctly handle the .requiresAction status and return the user to the appropriate screen after authentication.

What Is Included in the Work (Deliverables)

Process and Timeline

We start by clarifying the business model: subscriptions, one-time purchases, consumables, freemium. The architecture depends on this. Testing IAP requires Sandbox accounts (Apple) and License Testers (Google)—this is a separate environment setup.

Apple's Sandbox behaves differently from production: subscriptions renew every 5 minutes instead of monthly, inGracePeriod works differently. It is essential to test scenarios: trial expiration, cancellation, billing retry, refund.

The cost is calculated individually based on the set of tools and complexity of server-side logic. On average, we fit within a budget for a typical integration, but the savings from preventing errors and churn offset this investment within a few months.

Get a consultation for your project—contact us. We will help you choose the optimal payment architecture that passes store reviews and does not break under peak loads.