MAIBank

MAIBank is the consumer mobile banking product for Moldova Agroindbank (MAIB), the country's largest bank, built at Red River Apps. It is not one app but a small platform: a native Swift iOS app, a native Java Android app, a Java backend the apps talk to, and a shared repository of Protobuf schemas that is the single source of truth for every request and response across all three. By 2018–2019 it had passed 500,000 installs.

For an end user - a MAIB retail customer - it is everyday self-service banking on the phone: log in with a 5-digit PIN or biometry, see balances across current, credit, and deposit accounts, browse a cards carousel and block or unblock a card instantly, move money by P2P (person-to-person), card-to-card, or account-to-account transfer, pay utility and provider bills, withdraw cash from an ATM without a card via a one-time code ("Cash-by-Code"), review a paged transaction history with a custom date-range calendar, and find the nearest branch or ATM on a clustered map. Sensitive actions are confirmed with an SMS one-time password.

I was the main iOS contributor, and also worked on the shared Protobuf contract and the Java backend, from December 2017 to May 2019. The iOS app is Swift on classic UIKit / MVC with storyboards, manual dependency injection through singleton managers, and a dedicated migration layer that moves legacy users onto the new biometric / PIN security model.

The defining platform decision is that the whole thing speaks binary Protocol Buffers over HTTP instead of JSON / REST. Every DTO is defined once in a shared .proto contract and code-generated per platform in CI - Swift for iOS, Java for Android, and Java for the backend - giving a compact, strongly-typed, versioned wire format (an uncommon choice for a 2018-era mobile bank). The backend itself is distributed rather than monolithic: a customer-facing API (SparkJava / embedded Jetty over raw JDBC), a separate Spring Boot admin console, and a standalone push-notification microservice, all sharing one SQL Server database and the same contract.

A notable piece is the iOS secure storage. The local database is an encrypted Realm whose 64-byte key is wrapped two independent ways in the Keychain - once behind biometry (invalidated automatically if the enrolled fingerprints or face change) and once behind the PIN, which is stretched through PBKDF2-HMAC-SHA512 at 200,000 rounds - so either factor can unlock the vault and both bind the secret to the device, paired with TrustKit certificate pinning on a custom URLSession delegate. A built-in demo mode intercepts at the networking layer to serve canned Protobuf responses from a seeded database, enabling App Store review and offline demos with no live server.