Mobile App for Parking Payment Development

We develop mobile apps for parking payment. The key challenge is the session model: a parking session starts upon entry and ends upon exit or when purchased time expires. The user must know exactly how much time is left and receive a warning before penalties kick in. This requires precise push notifications, background timers, and reliable payment gateway integration.

Recently, we handled a case where a parking operator lost up to 15% of revenue (about 1.2 million rubles per year) due to unpaid extensions. Users forgot to extend, and push notifications didn't always arrive. We developed an app that solved this: added SMS duplication, improved the timer, and implemented automatic extension. Result: fines dropped by 95%, extension conversion rose by 40%. Savings for the operator: over 500,000 rubles in the first quarter.

Our experience: over 7 years in mobile development, dozens of implemented parking solutions. We guarantee the app passes App Store and Google Play moderation on the first attempt, including privacy requirements (ATT, Privacy Nutrition Labels) per App Store Review Guidelines Section 4.2.

Contact us to discuss your project and get a demo. Order a consultation to estimate the scope of work.

Apple Vision Framework documentation

How to organize session management in a parking payment app?

The central entity is ParkingSession. It has a lifecycle:

IDLE → ACTIVE → EXPIRING (15 min before end) → EXPIRED / EXTENDED

State transitions are managed on the server. The app displays the current state via polling or WebSocket. The local timer is for UI only, not for business logic.

A typical session object:

{
  "sessionId": "PSN-SESSION-4471",
  "zoneCode": "A-12",
  "vehiclePlate": "А123ВС77",
  "startedAt": "2024-07-15T10:15:00+03:00",
  "expiresAt": "2024-07-15T12:15:00+03:00",
  "rate": 60,
  "currency": "RUB",
  "status": "ACTIVE",
  "paymentStatus": "PAID"
}

Why is accurate session state synchronization important?

A mismatch between server time and local timer can cost the user a fine. Therefore, we use server time as the single source of truth. The local counter is only for display. Each time the app opens or receives a push, the session is re-fetched from the server. For critical notifications (5 minutes before expiration), we duplicate sending via FCM and SMS if push is undelivered (optional).

License plate recognition via camera — mobile app development

Manual plate entry is poor UX. Camera recognition is better. On iOS we use Vision + VNRecognizeTextRequest. On Android — ML Kit Text Recognition. Recognition accuracy for Russian plates on good images is around 85–90%. For tough cases, we use server-side OpenALPR.

import Vision

func recognizePlate(from pixelBuffer: CVPixelBuffer) {
    let request = VNRecognizeTextRequest { [weak self] request, error in
        guard let observations = request.results as? [VNRecognizedTextObservation] else { return }

        let candidates = observations.compactMap { $0.topCandidates(1).first?.string }
        let plateRegex = /[АВЕКМНОРСТУХ]{1}\d{3}[АВЕКМНОРСТУХ]{2}\d{2,3}/
        let plate = candidates.compactMap { $0.firstMatch(of: plateRegex)?.0 }.first

        DispatchQueue.main.async {
            self?.vehiclePlateField.text = plate.map(String.init) ?? ""
        }
    }
    request.recognitionLevel = .accurate
    request.recognitionLanguages = ["ru-RU"]

    let handler = VNImageRequestHandler(cvPixelBuffer: pixelBuffer)
    try? handler.perform([request])
}

How to ensure reliable push notification delivery in a parking payment app?

One common problem is push loss due to iOS power saving mode or Android Doze. We solve this through:

• high-priority FCM messages with a collapsing key to avoid notification duplication;
• SMS duplication for critical situations (optional);
• a local fallback timer that fires if no server response arrives 2 minutes before the deadline.

The countdown timer is the most requested UI element. On iOS it lives in ProgressView + Timer, on Android in CountDownTimer. But background notifications go through APNs/FCM.

Server-side notification logic:

• 15 minutes before expiresAt → push "Parking expires in 15 minutes"
• 5 minutes before → push with buttons "Extend by 1 hour" / "End"
• At expiresAt → push "Parking session ended"

On iOS, buttons in push notifications are implemented via UNNotificationCategory. Pressing "Extend" from the notification opens the app on the extension screen and automatically initiates payment with a saved card without extra steps.

How to integrate the app with a payment gateway?

Parking payment has two scenarios:

Pre-paid — buy time before entry. User selects zone, time, pays. Server issues a session code. At entry, an operator scans a QR or reads the plate.

Post-paid — pay at exit. Session starts automatically upon entry (by plate), amount calculated at exit, app prompts payment.

Comparison:

For both scenarios, we use a saved card via a provider token (CloudPayments, YooKassa, Stripe). One-time payment without saving card: via a payment web widget in WKWebView/WebView. Regular payments (subscription): via recurring payments with a token.

Integration with parking equipment

If the parking lot uses an access control system or barrier, integration is through the operator's server API. Common protocols: SOAP/XML (legacy), REST JSON (modern). The app does not talk to equipment directly — only via the backend.

For barrier opening via QR code at exit, we use AVCaptureSession.

What's included in the development?

We deliver a complete package:

• Architectural documentation (diagrams, API description)
• Source code with unit test coverage (>70%)
• CI/CD setup (GitHub Actions, GitLab CI)
• Integration with payment gateway and parking API
• Publication to App Store and Google Play (including screenshots, descriptions)
• Admin and user manuals
• Technical support for 2 weeks after release
• Access to repository and task management system
• Training for the operator's team on the admin panel

How does the development process work?

We follow these stages:

1. Requirements analysis and prototyping (3 days)
2. Architecture and API design
3. MVP development with core features
4. Integration with payment gateway and parking API
5. Testing (unit >70%, integration, UI)
6. Publication to App Store and Google Play

Base version (sessions, timer, card payment, push): 4 to 6 weeks. Adding plate recognition, equipment integration, subscriptions: another 2 to 4 weeks. Cost is calculated individually after requirements analysis.

Contact us to discuss your project — we'll prepare a prototype in 3 days and propose an optimal solution. A separate consultation on architecture and integrations is also available. Order development and get a finished app on time.

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.