CRM Integration with Mobile Apps: BFF, Offline, Push

If your sales department uses a CRM, a mobile app without integration becomes manual data entry, lost deals, and duplicated tasks. We connect the app with the CRM through a BFF proxy, ensuring instant synchronization, offline mode, and push notifications. For example, when a deal status is updated via the web interface, the app receives a notification within 2-3 seconds. According to our practice, integration pays off in 2-3 months by reducing manual entry by 80%. Get a free assessment of your project — contact us.

How to Choose the Right Integration Approach for CRM and Mobile App?

Direct connection to CRM API from a mobile app is risky. API keys are stored in APK or IPA (easily extracted via jadx or class-dump), business logic is uncontrolled, and caching is absent. The correct architecture: mobile app → custom API (BFF, Backend for Frontend) → CRM. BFF keeps secrets on the server, transforms data for the mobile client.

BFF returns only what the specific screen needs: a list of deals with name, amount, and status — not the entire object with 40 fields. This reduces traffic and parsing time by 3x. The pattern is described on Wikipedia.

Why BFF is Better Than Direct Connection

BFF isolates CRM specifics: when switching CRM (amoCRM → Bitrix24), you only rewrite the adapter, not the entire app. Additionally, BFF allows versioning the API for the mobile client without affecting other systems. Our engineers use Kotlin/Spring Boot or Go, depending on load. Typical BFF implementation is 100-150 lines of code per entity, speeding up development by 40%.

How to Ensure Offline Mode?

A sales rep drives to a client — internet drops. They make a call, record agreements in the app, data must be sent to CRM when network returns. On Android we use WorkManager with NetworkType.CONNECTED, on iOS — BGProcessingTask. Local storage (Room or Core Data) buffers changes; when connection is restored, the worker sends packets to BFF.

Conflicts: if a manager changed the deal via web while a mobile user was offline, data diverges. A simple strategy is server-wins (CRM overwrites local). More complex: versioning via updated_at timestamp with user choice on conflict. The chosen strategy affects implementation complexity by 20-30%.

Notifications About Changes

CRM changes deal status — the app must know. Compare methods:

WebSocket has 10x lower latency than polling but requires persistent connection. For most CRM scenarios, polling with a 1-2 minute interval strikes a good balance. Webhook → Push is preferred if CRM supports external callbacks.

Typical Entities and Mapping

Each CRM calls objects differently. Mapping in BFF:

A unified model in the app (Deal, Contact, Company) with adapters per CRM in BFF — allows supporting multiple CRMs or switching CRM without rewriting the client. Budget savings on re-integration up to 60%.

What Is Included?

• Detailed analysis of integration scenarios (sync, notifications, offline).
• BFF design with documented API (Swagger/OpenAPI).
• Implementation of adapters for 1-3 CRMs (additional ones by agreement).
• Offline mode and background sync setup.
• Push notification integration (FCM/APNs).
• Testing on real scenarios (App Store Review Guidelines, Google Play).
• Handover of access and maintenance instructions.

Timelines and Guarantees

Basic integration with one CRM via BFF, CRUD operations, offline buffer: 2-4 weeks. Adding push notifications, conflict resolution, multi-CRM support: plus 1-2 weeks. Cost is estimated individually.

Our experience: 5+ years in mobile development, 30+ implemented CRM integrations. We guarantee stable operation post-launch. Get a consultation — contact us. Order a free integration audit — we'll estimate timelines and cost.

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.