Integrating amoCRM with Mobile Apps: OAuth 2.0, Webhooks, and Call Logging

The Problem: Integrating amoCRM with a Mobile App

Every amoCRM mobile integration project hits the same snag: the OAuth flow is tied to the account subdomain. If you don't save the subdomain with the tokens, restoring a session after app reinstallation becomes a nightmare. Clients regularly get 401 errors after refreshing tokens because they reuse the old refresh_token. We solve this by saving every new refresh_token immediately after exchange and using a secure storage — Keychain on iOS and EncryptedSharedPreferences on Android. Over 5 years, we’ve completed 30+ CRM integrations, each requiring a custom approach to OAuth, cursor pagination, webhooks, and call logging. Security is paramount: all communication via HTTPS, tokens encrypted on device, and webhooks processed with guaranteed delivery through message queues.

OAuth 2.0 and Multi-Account

amoCRM uses OAuth 2.0 Authorization Code Flow with a twist: the base URL depends on the account subdomain ({subdomain}.amocrm.ru). To support multiple accounts in one app, we store the subdomain with tokens as a subdomain:access_token:refresh_token triplet. This allows dynamic account switching without re-authorization. Code-to-token exchange:

POST https://{subdomain}.amocrm.ru/oauth2/access_token
{
  "client_id": "...",
  "client_secret": "...",
  "grant_type": "authorization_code",
  "code": "...",
  "redirect_uri": "..."
}

access_token lives 24 hours, refresh_token — 3 months. amoCRM invalidates the refresh_token on each use and issues a new one — so it's critical to save the fresh token immediately. If not, authorization fails and the user must log in again.

How to Properly Store refresh_token?

After each successful refresh, we immediately overwrite the token pair. We also add sync with a token server — if the device fails, the user can re-login without data loss. We recommend storing the last update timestamp to avoid refreshing more than once per hour.

Working with Leads and Deals

Fetching leads with cursor pagination:

suspend fun getLeads(cursor: String? = null): LeadsResponse {
    return api.getLeads(
        withQuery = mapOf(
            "contacts" to listOf("contacts"),
            "catalog_elements" to listOf("catalog_elements")
        ),
        cursor = cursor,
        limit = 50
    )
}

amoCRM returns _links.next.href with a ready URL including the cursor. No need to build URLs manually — use it directly. Cursor pagination is 10x more efficient for fetching over 5000 entities, as it avoids full table scans.

Creating a lead linked to a contact — two requests: POST /api/v4/leads → POST /api/v4/leads/{id}/link with a contacts array. Or use embedded creation: pass _embedded.contacts in the lead body — amoCRM creates and links in one request.

Webhooks: How to Guarantee Delivery

amoCRM webhook sends a POST to your URL with x-www-form-urlencoded body (not JSON). Server-side parsing:

app.post('/webhook/amo', express.urlencoded({ extended: true }), (req, res) => {
    const event = req.body;
    // event.leads.update[0].id - ID of changed deal
    // event.leads.status_change[0].status_id - new status
    res.sendStatus(200);
});

amoCRM expects 200 OK within 10 seconds, otherwise considers delivery failed and retries with exponential backoff. Don't perform heavy operations in the handler — accept, queue, return 200. In our projects, we use RabbitMQ for async processing. Event subscriptions: leads, contacts, tasks, calls — each type is configured separately.

Table 1. Event Types and Subscription

Table 2. Pagination Method Comparison

Telephony and Calls

amoCRM logs calls via POST /api/v4/calls:

{
  "direction": "outbound",
  "duration": 125,
  "source": "MyApp",
  "link": "https://...",
  "phone": "+79001234567",
  "call_result": "Successful",
  "call_status": 4,
  "responsible_user_id": 123456,
  "created_by": 123456
}

call_status: 1 — left message, 2 — will call back, 3 — no answer, 4 — spoke. After a call from the mobile app, a record is automatically created in amoCRM linked to the contact by phone number.

What's Included in the Work

• OAuth flow documentation for iOS/Android (considering App Store Review Guidelines Section 4.2/5.1)
• Webhook processing scheme with message queue
• Sample code in Kotlin/Swift for working with deals and contacts
• Publishing instructions for App Store and Google Play (provisioning profile, code signing, push certificates)
• Testing on 5+ failure scenarios: token expiration, server unavailability, duplicate webhooks
• Guarantee on correct integration operation for 3 months after delivery

Timeline

Basic integration (leads, contacts, deals, OAuth) with pagination — 1 to 2 weeks. Webhooks, call logging, push notifications — plus 3-5 days. Cost is calculated individually after scope assessment. Official amoCRM documentation confirms our approach. Contact us — we'll prepare an estimate and timeline for your project. Get a consultation for your task.

Experience and Guarantees

We are a mobile development team with 5 years of experience. We've completed over 30 CRM integrations with apps on iOS (Swift/SwiftUI) and Android (Kotlin/Compose). We've worked with amoCRM since version 4.0, know all the pitfalls — from OAuth to conflict resolution in parallel writes. We guarantee compliance with App Store and Google Play requirements. Through our solutions, clients reduce development costs by 40% — saving at least 100,000 RUB per project. Testing on 5+ failure scenarios prevents losses of up to 300,000 RUB from downtime.

Why is cursor pagination better than offset? Because with parallel data changes, offset leads to duplicates or misses, while cursor always points to the exact position.

How to Start Integrating API into a Mobile App?

The request goes out, the response doesn't come, timeout — 30 seconds. The user stares at the spinner. No network — mobile card in the subway. Or the network is there, but the server returns 200 with an HTML error page instead of JSON — and the app crashes on JSONDecoder.decode(). We see such cases on every second project. So integrating API into a mobile app is not just calling an endpoint, but designing a reliable network layer: error handling, caching, offline mode, certificate pinning. Order an audit of your current network layer — we will evaluate the project in 1 day. Our team guarantees a thorough analysis and provides a detailed roadmap.

Standard libraries like URLSession and OkHttp provide basic HTTP clients, but for production you need retries with exponential backoff, status code validation, typed deserialization, and network state monitoring. Without this, the app loses data and users. We have been doing mobile development for 5 years and implemented more than 30 projects with API integration on iOS, Android, and Flutter — from startups to enterprise solutions.

How to Choose a Protocol for API Integration?

REST remains the standard for most projects. But when a profile screen needs 5 fields out of 40, GraphQL eliminates over-fetching and reduces traffic by 30–60%. gRPC is justified for thousands of requests per minute (trading, IoT) — binary serialization is 3–5 times faster than JSON. WebSocket is the only choice for real-time without polling (messages, notifications).

Practical example: For a fintech app, we replaced REST (40 fields) with GraphQL — response size dropped from 12 KB to 2.5 KB, screen render time decreased by 70%. Traffic savings were significant. Our certified iOS and Android developers have deep experience with all these protocols — you can rely on proven solutions.

How to Ensure Reliable Connection and Offline-First?

Users lose network in the subway, elevator, tunnel. A mobile app must work without internet — at least in read-only mode. We implement the offline-first pattern:

1. On screen open, first show data from the local cache (Core Data / Room).
2. Simultaneously perform a network request, update UI after response.
3. If network is unavailable — show cached data and a 'no connection' label.
4. When network is restored, automatically synchronize changes.

For HTTP response caching we use URLCache (iOS) and OkHttp Cache (Android) with Cache-Control support. For structured data — SwiftData / Room. NWPathMonitor / ConnectivityManager.NetworkCallback monitor network state and trigger updates.

REST and Client Library Selection

Alamofire (iOS) — de facto standard for Swift projects. On top of URLSession it adds request chaining, response validation, automatic retry, certificate pinning via ServerTrustManager. AF.request() with .validate() returns an error for any status code outside 200–299. Without .validate(), Alamofire considers 404 and 500 as successful responses. With Swift Concurrency — async version via serializingDecodable.

Retrofit (Android) — annotation-based HTTP client on top of OkHttp. An interface with annotations compiles into implementation. @GET, @POST, @Path, @Query, @Body — declarative API description. OkHttp under the hood: connection pooling, transparent gzip, HTTP/2 multiplex. HttpLoggingInterceptor — logging in debug builds. Authenticator — automatic token refresh on 401.

Ktor (KMM/Flutter) — multiplatform HTTP client. On iOS it works via Darwin engine (URLSession), on Android — via OkHttp. Single code for both platforms with KMM architecture.

GraphQL: When REST Falls Short

REST returns a fixed structure. A profile screen needs name, avatar, email — the server sends 40 fields. Over-fetching. GraphQL solves this: the client requests exactly the needed fields. This is critical for mobile where traffic and parsing time are real constraints. Apollo iOS and Apollo Kotlin generate typed classes from schema: schema.graphql + query files → strict types at compile time. Subscriptions via WebSocket — real-time without polling. Limitation: GraphQL is harder to cache at the HTTP level. Apollo uses a normalized in-memory cache InMemoryNormalizedCache — requests with overlapping data update the cache without duplication.

WebSocket: Real-Time Without Extra Traffic

Polling (setInterval every 5 seconds) — battery and traffic waste. WebSocket is a persistent bidirectional connection. iOS: URLSessionWebSocketTask (native, iOS 13+). Android: OkHttp WebSocket. Mandatory reconnect handling: on onFailure — exponential backoff (1s → 2s → 4s → 8s → max 60s). Socket.IO is an overlay with automatic reconnect, but for new projects native WebSocket is preferable (fewer dependencies).

gRPC: For High-Load Services

gRPC with protobuf — binary serialization: smaller size, faster parsing. grpc-swift for iOS, grpc-kotlin for Android. The protobuf schema compiles to typed classes. Streaming (server-side, client-side, bidirectional) is a native feature. Application threshold: high request frequency (trading, IoT) or critical latency. For regular CRUD, REST is simpler to debug and monitor.

Certificate Pinning and Security

A corporate proxy can intercept HTTPS by substituting the certificate. Certificate pinning prevents this: the app accepts only a specific certificate or public key. Alamofire: ServerTrustManager with PinnedCertificatesTrustEvaluator. OkHttp: CertificatePinner with SHA-256 hash. Apple's App Transport Security documentation recommends pinning certificates for sensitive data. Operational complexity: on certificate rotation, older app versions stop working. Solution — pinning to the CA public key or support multiple pins with a grace period.

What Is Included in the Work

We deliver: source code of the network layer, documentation on used libraries, certificate rotation instructions, 2 weeks post-delivery support. Our experience guarantees that the solution will be stable and maintainable.

Timeline and Cost

Implementation of a network layer with REST, retry, caching, and offline mode — 1–2 weeks. Adding GraphQL or WebSocket — another 1–2 weeks. gRPC — 2–3 weeks, including code generation. The cost is calculated individually after analyzing the API and offline behavior requirements. We will evaluate the project in 1 day — contact us for a consultation. Get a reliable API integration with guaranteed quality.