iOS App Migration & Long-Term Maintenance for a Japanese Tech Company

Project Snapshot
Client	Company C (anonymized) · Technology sector, Japan
Industry	Technology
Category	Software Outsourcing / Mobile Development (iOS)
Location	Japan
Team Size	2 engineers
Phase	Coding · Unit Testing · Ongoing Maintenance
Date	Commenced 2022 · Continuing labo project

Sonix partnered with Company C to rescue and modernize a production iOS application that had fallen several major Swift versions behind. The engagement covers a full migration from Swift 2 to Swift 5.3.2, ongoing maintenance, and the continuous delivery of new features — keeping the app stable, performant, and ready for the latest iOS ecosystem.

— Why Sonix

Why Company C Chose Sonix

📱

Deep iOS Expertise

Sonix engineers have hands-on experience across the full Swift version lifecycle, making multi-generation migrations a manageable, structured process rather than a disruptive overhaul.

🤝

Japan-Ready Communication

With a bilingual team and a strong track record serving Japanese clients, Sonix bridges language and cultural gaps with clear reporting, structured sprints, and reliable Backlog-driven coordination.

🔄

Long-Term Labo Model

Rather than a one-off handoff, Sonix operates as an embedded development partner — continuously maintaining, testing, and extending the app as requirements evolve alongside the client’s business.

— The Challenge

A Legacy Codebase at Risk

Company C had an iOS application in active use — but it was built on Swift 2, a version that Apple had deprecated and that Xcode no longer fully supported. Continuing to develop or even maintain the app on this foundation carried compounding risks: incompatible APIs, ABI instability, deteriorating performance, and an ever-widening gap with modern iOS platform capabilities.

The client needed a team capable of safely navigating the migration through multiple Swift versions — not just updating syntax, but refactoring deprecated patterns, modernizing the SQLite data layer, and ensuring continuity so users never experienced disruption. Post-migration, ongoing maintenance and feature expansion would also need to be sustained under the same partnership.

— Our Approach

How We Approached the Migration

Codebase Audit & Migration Roadmap

We began with a thorough audit of the existing Swift 2 codebase, cataloguing every deprecated API call, unsupported syntax pattern, and third-party dependency that required attention. This formed the basis of a phased migration plan — incremental version jumps from Swift 2 to 3, then 4, and finally to 5.3.2 — each verified before proceeding to the next, reducing the risk of cascading breakages.

Code Modernization & API Refactoring

Beyond straightforward syntax updates, we refactored the app’s architecture to leverage modern Swift idioms — value semantics, optionals handled properly, async-safe patterns, and SwiftUI-compatible structures where applicable. The SQLite data layer was restructured for stability and query efficiency. Unit tests were written alongside each refactoring pass to catch regressions early.

Continuous Maintenance & Feature Delivery

With the migration complete, Sonix transitioned seamlessly into an ongoing labo engagement — managing version updates, addressing bugs, and delivering new functionality in iterative cycles. All work is tracked via Backlog and Git, ensuring full transparency and traceability for the client team throughout.

— The Solution

A Modernized, Future-Ready iOS App

Sonix executed a comprehensive migration of Company C’s iOS application from Swift 2 to Swift 5.3.2, transforming a fragile legacy codebase into a stable, maintainable product aligned with current Apple platform standards. The migration involved systematic replacement of deprecated UIKit APIs (including legacy alert and networking patterns), full adoption of Swift’s modern type system, and optimization of the SQLite integration layer for reliability and performance.

The delivery didn’t stop at migration. Under an ongoing labo model, the Sonix team continues to serve as Company C’s dedicated iOS development resource — implementing new features, managing iOS version compatibility as Apple releases updates, and maintaining code quality through consistent unit testing practices. The entire workflow is managed transparently through Git version control and Backlog project tracking, giving the client full visibility and control at every stage.

— Technologies

Technologies Used

Swift 5.3.2
iOS (UIKit)
Xcode
SQLite
Git
Backlog
XCTest (Unit Testing)

— Results

What We Achieved Together

100%

Migration Completed

Full codebase successfully migrated from Swift 2 to Swift 5.3.2 with zero production downtime

Years of Partnership

Ongoing labo engagement since 2022, delivering continuous maintenance and new feature development

Stable

Modern iOS Platform

App now runs on current iOS APIs with full ABI stability, improved performance, and an expanded feature set

— Key Features

What Was Delivered

Feature	Description
Multi-version Swift Migration	Staged, incremental upgrade path from Swift 2 through to Swift 5.3.2, with validation at each version checkpoint before proceeding.
Deprecated API Replacement	All legacy UIKit APIs (UIAlertView, UIWebView, and others) replaced with their modern equivalents to ensure Xcode compatibility and App Store submission readiness.
Code Optimization	Refactored core logic to leverage modern Swift idioms — improved optionals handling, value types, protocol-oriented patterns — reducing technical debt and improving maintainability.
SQLite Layer Modernization	Restructured database access layer for improved query performance, thread safety, and compatibility with Swift’s modern concurrency model.
Unit Testing Suite	Comprehensive XCTest-based unit tests written during migration to verify behaviour, catch regressions, and provide ongoing confidence in each subsequent release.
New Feature Development	Post-migration labo work includes delivery of additional app capabilities as defined by Company C’s evolving product roadmap.
Transparent Project Management	All work tracked via Backlog and Git, giving the client full visibility into task status, commit history, and release planning.

“

— Client Testimonial

“When we brought in Sonix, our iOS app was already struggling to keep up with new Xcode releases — it was only a matter of time before we couldn’t ship updates at all. The team handled the entire migration methodically, keeping us informed at every step, and the app came out the other side noticeably more stable and faster. What impressed us most was how smoothly they adapted to our workflow and continued adding features without missing a beat. We have kept working with Sonix since the migration completed, and we fully intend to continue doing so.”

— Project Manager, Company C · Japan

Sonix — Your success is our happiness.