Dynamic Gas Fee Calculation for Mobile Wallets: Save Time and Money

When sending a transaction, users face a dilemma: which fee to choose? Too low — the transaction can get stuck for hours; too high — overpaying several times. Many wallets use fixed values, leading to losses or delays. Our team, with 5 years of experience, develops algorithms that analyze current network load and offer optimal fees in three modes. This saves users money and time.

For example, one of our clients — a crypto wallet with 100,000 users — after implementation reduced average confirmation time by 40% (compared to static fee wallets) and decreased the number of stuck transactions by 80%. Fee savings reached up to 30% for active traders. Our integration typically costs between $2,000 and $5,000, and clients often save over $1,000 per month in overpaid fees.

Why Dynamic Transaction Fee Calculation Matters

Network fee directly affects user experience. If the wallet shows too high a fee, the user leaves. If too low — the transaction stalls. The key tools are eth_feeHistory (EIP-1559) and eth_gasPrice for legacy networks. Without them, accurate calculation is impossible.

For Ethereum Mainnet, we use eth_feeHistory with percentiles 10, 50, 90 over the last 10 blocks. This gives a realistic picture of network load. Below is an example request in Kotlin/Android via web3j:

val feeHistory = web3j.ethFeeHistory(10, DefaultBlockParameterName.LATEST, listOf(10.0, 50.0, 90.0)).send()
val baseFee = feeHistory.feeHistory.baseFeePerGas.last()
val slowPriorityFee = feeHistory.feeHistory.reward[0][0]
val avgPriorityFee = feeHistory.feeHistory.reward[0][1]
val fastPriorityFee = feeHistory.feeHistory.reward[0][2]

For iOS, similar logic on web3swift:

let feeHistory = try await web3.eth.feeHistory(blockCount: 10, newestBlock: .latest, rewardPercentiles: [10, 50, 90])
let baseFee = feeHistory.baseFeePerGas.last!
let slowPriority = feeHistory.reward[0][0]
let avgPriority = feeHistory.reward[0][1]
let fastPriority = feeHistory.reward[0][2]

For Polygon, we use the Gas Station API — it adapts to local gas spikes.

How the Three Modes Work: Slow / Average / Fast

The user selects a confirmation speed. The app automatically calculates maxFeePerGas = baseFee * multiplier + priorityFee. The multiplier and priority fee percentile define the mode:

The final cost is converted to USD at the current ether price. For ETH-transfer, gasLimit is fixed at 21000. For contracts — eth_estimateGas with a 20% buffer. For complex smart contracts, we execute eth_estimateGas in each block, adding a 20% buffer for unforeseen opcodes. The result is multiplied by the elevated baseFee for Fast mode to guarantee execution.

Choosing the Optimal Provider for Gas Fee Calculation

The choice of provider (Infura, Alchemy, QuickNode) affects speed and accuracy of data. We recommend Alchemy for mainnet — their API returns eth_feeHistory with low latency. For testnets, Infura is sufficient. It's important to set up polling feeHistory with an interval of 10–15 seconds to keep data up-to-date.

What Is Manual Tuning and How to Implement It?

Custom mode — fields maxFeePerGas and maxPriorityFeePerGas in Gwei. Validation:

• maxPriorityFeePerGas cannot exceed maxFeePerGas
• maxFeePerGas must be at least current baseFee (otherwise the transaction will stall)
• Warning for very low values

Input in Gwei is more convenient: 1 Gwei = 10^9 Wei.

Testing Gas Fee Correctness

We test on mainnet and testnets (Goerli, Sepolia). We simulate different network loads, check confirmation time for each mode. We monitor transactions on Etherscan. All calculations are compared with real data. Results are documented in a report.

What Results We Guarantee

In 5 years on the market, we have completed over 50 projects related to crypto wallets, including gas fee integration for Ethereum, Polygon, BNB Chain, and other networks. Our clients save up to 30% on fees thanks to accurate calculation. Users get transparent fees and predictable confirmation times.

What's Included in the Work

Work Process and Timelines

1. Analytics — study current wallet architecture, select provider (Infura, Alchemy).
2. Design — blockchain interaction protocol, speed UI/UX.
3. Implementation — calculation code, API integration, custom settings interface.
4. Testing — simulation of various network loads.
5. Deployment — upload to App Store/Google Play.

Estimated time: 2 to 5 days, depending on complexity. Cost is calculated individually. Contact us to evaluate your project. Order gas fee calculation integration into your wallet — users will appreciate transparent fees. Get a consultation on integration today.

Source: Ethereum Documentation on Gas

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.