A React Native cross-platform mobile app with appointment booking, lab result downloads and push notifications. 60% of appointments now happen in the app, and call-center load dropped 24%.
Background
The client is a Hungarian private healthcare provider with 8 Budapest clinics, 30+ medical specialties and 15–20 thousand active patients. The web customer portal worked, but a growing share of patients wanted mobile access, particularly for appointments.
The existing flow: web portal or call-center phone call. The call center handled 200–250 calls daily, of which 60–70% were routine (booking, cancelling, modifying). The client's goal: reduce call-center load and increase patient satisfaction.
Challenge
Healthcare mobile apps carry two serious challenges. (1) GDPR and Hungarian healthcare data handling: patient data is especially sensitive, auth and data storage are strictly regulated. (2) The 60+ user segment is 35% of the base — UX must be accessible for non-tech users while the younger segment expects a premium feel.
On the tech side, the existing customer portal ran on SQL Server with a .NET API. We didn't want to rewrite the existing API, but a few new endpoints were needed (push token registration, lab result download). The mobile app and the portal needed to work independently.
Approach
We chose React Native because the client didn't want double native development cost. React Native's limits (push notifications, camera, biometric auth) can be covered well with Expo modules and custom native modules where needed.
Discovery was 3 weeks, with 1 week of user interviews in the 60+ segment. Lessons: larger font sizes, higher contrast, fewer modal dialogs. In the wireframe phase we tested two versions on paper prototypes with 8 participants.
Solution
Main React Native features: (1) Appointment booking (specialty, doctor, time, location), (2) Existing bookings list with modify and cancel options, (3) Lab result download and inline viewing (PDF renderer), (4) Push notifications (booking reminder, result delivery), (5) Profile and personal data management.
Backend integration runs against the existing .NET API plus 4 new endpoints for mobile-specific features. Auth uses Microsoft Entra ID (the patient portal also uses it). Push notifications go via OneSignal, with token registration refreshed on every login. Lab results are encrypted at rest and only downloadable within the current session.
Tech decisions
React Native vs Flutter: the client's team had React experience (web portal is Next.js), so code-sharing and team flow favored React Native. Flutter was an option, but the learning curve made React Native the winner.
Expo vs bare React Native: we started in Expo managed workflow, later migrated to bare because OneSignal native module integration required it. Modular over-the-air updates (Expo EAS Update) stayed — small bug fixes ship in 10–15 minutes without store submission.
Firebase Crashlytics + Sentry: Crashlytics is limited on the free tier; Sentry has much better error grouping. We use both in parallel (Crashlytics integrated with Play Console, Sentry on the dev dashboard).
Bumps
First hurdle: 60+ segment UX. The MVP's bottom-sheet flows confused users (it wasn't obvious how to close them). We replaced them with full-screen modals and an explicit 'Close' button — a small visual compromise on modern UI conventions, but UX tests pointed that way.
Second: the App Store review bounced the first submission because the lab result feature had medical-device-claim-style language in the metadata. We rewrote the copy (information access, not 'medical advice'), and the second submission passed.
Third: the .NET API's legacy endpoint rate limits. Push token refresh on login from all clients arrived at once — the backend team introduced a queue-based processing because a rewrite didn't fit the scope.
Results
Six months after launch: 8500+ active users, 45% adoption against the 15–20 thousand active patient base. 60% of appointments are booked via mobile (call center 35%, web portal 5%). Call-center load dropped 24% (41% for routine bookings).
Crash-free user metric is 99.7% (Crashlytics + Sentry). App Store rating 4.6/5 (2400+), Google Play 4.5/5 (1800+). 60+ adoption rate is 28% (lower than 52% in the younger segment, but without the changes learned from interviews it would have been lower).
Stack
UX testing in the 60+ segment was the best decision. We initially wanted to launch 'a modern app', but real patient satisfaction depended on whether it could be used by people who rarely open apps.
CTO — Private healthcare
The quote represents typical client feedback; it is not a verbatim citation.
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