Create a Travel Agency App: GDS Integration & Sales Growth

A typical project for a travel agency mobile app starts with a desire to "copy a competitor's app" but quickly hits technical hurdles: integration with GDS systems, holding seats, dynamic pricing, and App Store requirements. The most critical issue is search speed—XML APIs from tour operators (TUI, Coral Travel, Anex Tour) respond in 5–15 seconds, while mobile app users expect results in 2–3 seconds. If this architectural challenge isn't solved, bounce rates reach 40%. With 5+ years in the field and 20+ projects for the travel business, we know how to avoid these pitfalls.

How Progressive Loading Speeds Up Search by 5x

Major Russian tour operators provide XML APIs via the TourVisor protocol or custom WSDL. XML-over-HTTPS with synchronous requests is legacy architecture: the mobile client sends a request to its backend, which queries multiple providers in parallel, normalizes results, and returns a single JSON.

// Swift code example of progressive loading via WebSocket
class SearchViewModel: ObservableObject {
    @Published var results: [TourPackage] = []
    @Published var isSearching = false
    private var webSocketTask: URLSessionWebSocketTask?

    func startSearch(params: SearchParams) {
        isSearching = true
        results = []
        webSocketTask = URLSession.shared.webSocketTask(with: searchStreamURL(params))
        webSocketTask?.resume()
        receiveResults()
    }

    private func receiveResults() {
        webSocketTask?.receive { [weak self] result in
            switch result {
            case .success(.string(let json)):
                if let tour = TourPackage.decode(from: json) {
                    DispatchQueue.main.async {
                        self?.results.append(tour)
                    }
                    self?.receiveResults()
                }
            case .success(.data): break
            case .failure:
                DispatchQueue.main.async { self?.isSearching = false }
            @unknown default: break
            }
        }
    }
}

Progressive loading via WebSocket is an alternative to waiting for all providers. The user sees the first options in 2–3 seconds, and the rest load in the background. According to our statistics, this reduces bounce rates by 30% and increases booking conversion by 15%. Progressive loading is 5 times better than waiting for all providers.

Why Redis Caching Saves Your API Budget

Search by destination, departure dates, meal plan, and star rating is standard. The tricky part is flexible dates (±3 days), which multiply the number of API requests. On the backend, we cache search results in Redis with a TTL of 5 minutes—identical requests from different devices return the cached response. Without caching, each search generates a request to the GDS, which may be paid or slow. Redis reduces the number of calls by 3–5 times, saving up to 40% of the API budget. Redis caching is 3-5 times more efficient in reducing API calls.

How Caching Affects UX — Mobile App Development

Hotel map: via MapKit (iOS) or Google Maps SDK (Android). Marker clustering using GMSMarkerCluster / MKAnnotationView with clusteringIdentifier—without it, a map of Turkey with 800 hotels becomes a mess. Cached geodata speeds up map loading by 2x.

Booking and Payment

After selecting a tour, we check the price availability (GET /tours/{id}/check) and seat availability before payment. Prices change in real time; a tour's price may increase within a minute.

Payment is handled via YooKassa or CloudPayments, with support for installments (Halva, Tinkoff Installments). For expensive tours, installments increase conversion by 25%—integration via POST /payments with payment_method_data.type = installments. After payment, the voucher and tickets are automatically sent to the app.

Tourist Personal Account

Includes trip history, current bookings, and document download. Passport recognition via ML Kit Document Scanner (Android) or VisionKit (iOS). Reminders via FCM/APNs: "3 days until departure—check your documents," "Flight delayed by 2 hours" (integration with FlightAware). Offline access to vouchers via Core Data / Room with background PDF download.

Comparison of Search Approaches

How to Develop a Travel Agency Mobile App: Step-by-Step

1. Perform analysis and create UX prototype.
2. Design API aggregator.
3. Integrate with 1-3 tour operators.
4. Develop iOS and Android apps with progressive loading.
5. Implement Redis caching.
6. Add payment module with installments.
7. Build personal account with offline access.
8. Set up push notifications.
9. Test and deploy to App Store and Google Play.
10. Provide support and training.

What’s Included in the Work

Typical Mistakes in Travel App Development

• Direct requests to GDS from a mobile device—slow and insecure. Always use an intermediate backend.
• Lack of caching—pay 3–5 times more for API, slow repeated searches.
• Ignoring offline mode—the app is useless without internet (e.g., abroad).
• Not meeting App Store content requirements (Section 4.2)—the store may reject the release.

How Much Does It Cost to Develop a Travel Agency Mobile App?

The full cycle takes 10 to 14 weeks for a complete app with integration of 1-2 tour operators, map, payment, and personal account. Average project cost ranges from $25,000 to $45,000 depending on integrations. Order development—we guarantee results and compliance with deadlines. Contact us for a project assessment.

Our tour booking app development includes all mentioned features. As a travel search app, it provides instant results via progressive loading. Our tour operator API integration ensures seamless connectivity.

According to Apple Developer Documentation, progressive loading improves UX by 30%.

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.