Senior iOS Engineer · Jakarta, ID

Building the markets that move on iOS.

I'm Prawira Hadi Fitrajaya — a senior iOS engineer with deep, hands-on experience across US Stocks, ID Stocks, Mutual Funds, and CFD at Ajaib. I build real-time trading surfaces that feel fast, stay crash-free, and earn the trust of millions of traders.

View selected work Get in touch
6+Years shipping
99%Crash-free
2sP95 app start
90%+Test coverage
Scroll
Profile

An engineering leader who ships, refactors, & mentors.

Six-plus years across iOS development, fintech product engineering, and data analytics. I build trading experiences across US Stocks, ID Stocks, Mutual Funds & CFD at one of Indonesia's largest platforms — while mentoring engineers and driving architecture decisions.

My roots in data analytics at Shopee and Ruangguru taught me to connect technical decisions to business outcomes. Today I combine architectural vision with hands-on depth: mentoring junior-to-mid iOS engineers, running technical interviews from junior through senior, and raising the bar through code review. I leverage AI coding agents like AntiGravity as force multipliers, operating in a Human-in-the-loop model where I maintain full ownership of code quality and user experience, especially critical for mobile development.

  • Real-time trading systems
  • TCA architecture
  • Performance engineering
  • Team mentorship
By the numbers

Six years shipping production iOS at scale.

99%

Crash-free sessions

Across Ajaib & Ajaib Alpha — millions of trading sessions held to a 99% crash-free rate.

55+

Tasks shipped

Across US Stocks, ID Stocks, Mutual Funds & CFD — full-stack feature delivery from spec to production.

21%

Faster core trade page

415ms → 328ms on the buy/sell surface, on a more scalable architecture.

90%+

Test coverage

Code smells kept under 5% on SonarQube with 90%+ coverage across owned modules.

Quality Engineering

Closing the loop with production observability.

Writing code is only half the job. I rely on Sentry to act as a rigorous quality gate, alerting me to production issues early so they can be triaged and fixed before impacting users.

The Quality Loop

Code
AI Agent
Review
Ship
Sentry Monitor
Triage
Fix

Active Monitoring & Alerting

Crash-Free Sessions

App Hangs & ANR

HTTP Client Errors

UI Load Performance

Main Thread I/O

Watchdog Terminations

Focus Areas

Where I go deep on iOS.

Six domains I design, build, and mentor around — the substance behind the trading surface.

  1. 01

    Real-Time Trading Systems

    Multi-source WebSocket pipelines for ID & US markets — bid/ask streams, out-of-hours behaviour, and live charting under sub-second latency.

    WebSocket · Combine
  2. 02

    Composable Architecture

    Unifying TCA store patterns across the US Stocks app, plus navigation and bottom-sheet systems engineers actually enjoy extending.

    TCA · MVVM-C
  3. 03

    Performance Engineering

    Trimming cold-start and render cost — Texture for heavy lists, P95 app-start of 2s, and measurable load wins on the core trade page.

    Texture · Instruments
  4. 04

    Observability & Insight

    Sentry page-load tracing, alerting baselines, and Mixpanel event design. Acting as a rigorous quality gate to catch, triage, and fix production issues early.

    Sentry · Mixpanel · Quality Gate
  5. 05

    Mentorship & Craft

    Growing junior-to-mid iOS engineers, running technical interviews across levels, and raising the bar through review.

    Reviews · Interviews
  6. 06

    AI-Powered Development

    Heavy experience with AI coding agents (AntiGravity) integrated deeply with my Sentry quality loop: code → AI agent → review → ship → Sentry monitor → triage. From TDD implementation to agent-driven code reviews.

    AntiGravity · Sentry Quality Loop · TDD
Selected Work

Shipped across four markets at Ajaib.

US Stocks, ID Stocks, Mutual Funds & CFD — features and systems I designed, delivered, and shipped safely in production.

Flagship feature · end-to-end Shipped safely

Take Profit / Stop Loss

Owned TP/SL from tech spec to production — core ViewModel logic, the Buy-Limit order section, and full portfolio-level create / edit / cancel flows. Automated risk management for every US Stocks trader.

Tech SpecCore VMBuy LimitPortfolio TP/SL
Order lifecycle Shipped safely

Amend Order Flow

Buy & sell order amendment built on a unified TCA store — entry point, value carry-over & calculation logic, and a gradual rollout config.

BuySellGradual rollout
Real-time data Shipped safely

Live Price Sockets

Multi-source WebSocket pipeline for ID & US markets. Fixed bid/ask freezes, out-of-hours socket behaviour, and built a SPY real-time chart proof-of-concept.

WebSocketCombineSPY PoC
Architecture Shipped safely

TCA Store Unification

Proposed and led a refactor unifying The Composable Architecture store patterns across the US Stocks app — plus a new navigation & bottom-sheet system.

RefactorNavigation
Observability Shipped safely

Performance Instrumentation

Error monitoring across multiple apps, Sentry page-load tracking on core trading flows, base metrics for alerting, and Mixpanel event trackers — turning the trading surface observable and data-driven.

SentryError MonitoringMixpanelP95 Alerting
First-month win Shipped safely

Stock Transfer

Shipped the Stockbit stock-transfer flow within my first month — from spec and unit tests to production.

Ship-fastUnit tested
Products Shipped safely

Options & Derivatives

US Stock Options and CFD groundwork — searchable options, expiry-with-timestamp handling, and contract detail refinements.

OptionsCFD
ID Stocks — 55 tasks shipped Shipped safely

Stock Lite & Pro Trading

Led Stock Lite/Pro mode, trading limits (TL), fractional & GTC orders, and post-order UX — reshaping how millions trade ID Stocks.

Stock Lite/ProGTCTL OrdersFractional
ID Stocks — Beta platform Shipped safely

Project Beta: SDP & Market

Seasonality charts & filters, stock comparison with add/search/tracking, broker summary & flow, screener entry points, and running trade module.

SeasonalityComparisonBrokerScreener
ID Stocks — Advanced orders Shipped safely

Short Sell & Collateral

IDSS Short Sell, margin ratio display on order page, collateral transfer from Regular to IDSS account, and IDSS activation flows.

Short SellMargin RatioCollateral Transfer
ID Stocks — US Stock bridge Shipped safely

Cross-Market Features

US Stocks Watchlist on the Blue App, RDN buying power, 24/7 order visibility, full US Stocks listing, and KYC tracker integration.

WatchlistRDN BPIndex ETFAlpha Widget
Buy & Sell refactor Shipped safely
21% faster load

415ms → 328ms on the core trading page, plus a more scalable architecture.

Trajectory

From data analytics to trading systems.

  1. Senior iOS Engineer I

    Ajaib Mar 2024 — Present

    Building and scaling one of Indonesia’s largest trading platforms. End-to-end feature ownership across US Stocks, ID Stocks, Mutual Funds & CFD.

    • Architected new modules — Stock Lite, Copy Trade, Bundle Trade, Fast Trade, Collateral — and advanced order types (GTC, Short Sell, Options, Limit).
    • P95 app-start of 2s and 99% crash-free on Ajaib & Ajaib Alpha; code smells kept <5% (SonarQube) with 90%+ coverage.
    • Boosted Mutual Funds rendering with Texture; built Firebase Remote Config marketing campaigns; mentor engineers and run technical interviews.
    • Human-in-the-loop AI development: use AntiGravity agent to accelerate implementation while maintaining strict manual review for code quality and mobile UX excellence.

  2. iOS Engineer

    Mister Aladin · MNC Group Oct 2023 — Mar 2024

    Led SwiftUI development of the Aladin Mall e-commerce app — SPM dependency management, URLSession networking, and Supabase persistence across the full delivery lifecycle.

  3. iOS Developer

    The Fepi Dec 2022 — Oct 2023

    Owned the full iOS lifecycle to App Store release — UIKit components, Firebase backend integration, and Mixpanel analytics driving data-informed feature decisions.

  4. iOS Engineer

    KoinWorks Jun 2022 — Nov 2022

    Shipped new KoinBisnis features on an MVVM stack, revamped UI, and integrated third-party liveness detection with unit-test coverage.

  5. Consumer Research Associate

    Ruangguru Nov 2021 — May 2022

    Ran end-to-end research and NPS analysis, turning statistical findings into executable product and marketing recommendations.

  6. Data Analytics & Reporting — Retail Finance

    Shopee Jul 2019 — Oct 2021

    Built automated dashboards (Apps Script, Data Studio) and managed collection systems reaching ~1M users — where I learned to let data drive decisions.

Technical Writing

34 tech specs authored & owned.

I design before I build. A selection of the specifications I authored for the trading platform.

01

US Stock TP/SL — Portfolio Create, Edit & Cancel

 02

US Stock Architecture Refactor — Unifying TCA Store Patterns

 03

SPY Chart + WebSocket Real-Time Update — Proof of Concept

 04

US Stock Sentry Performance Instrumentation

 05

US Stock Amend — Buy & Sell Amendment Flow

 06

Trade Config per Asset — Fractional & Order Types

 07

RDN as US Stocks Buying Power

 08

Bid / Ask Visibility on Closed Market

 09

rolloutManager (Unleash Key) List — US Stock & US Stock Options

 10

Contract for Difference (CFD) — Commodity, Forex, Index
Toolkit

What I build with.

Languages & UI

  • Swift
  • Objective-C
  • SwiftUI
  • UIKit
  • Texture / AsyncDisplayKit

Architecture

  • TCA (Composable)
  • MVVM · MVVM-C
  • Combine
  • Swift Package Manager

Real-time & Data

  • WebSocket
  • URLSession
  • Firebase
  • Supabase

Quality & Insight

  • XCTest
  • SonarQube
  • Sentry
  • Mixpanel
EDU
B.Econ, Managerial Economics — Universitas Mercu Buana · Cum Laude 3.63/4.00
CERT
iOS Engineering & Full-Stack Web — Binar / SYNRGY Academy · BCA scholarship
Side Projects

What I build off the clock.

Independent iOS & full-stack projects — from fintech super-apps to real-time market dashboards.

Swift

Banking Super App

iOS fintech super-app concept — multi-account dashboard, transaction flows, and modular architecture.
TypeScript

Financial Market Insight

Crypto exchange market news and real-time data feed aggregator.
Swift

Simple Login App

Clean authentication flow — UIKit-based login with form validation and state management.
TypeScript

TMDB Web App

Movie database demo — search, browse, and discover films via the TMDB API with a responsive SPA.
Swift

TheMovieDBTest

Native iOS TMDB client — UIKit networking layer with result-driven architecture.
TypeScript

Fiery Juno

Full-stack web project — modern TypeScript stack with interactive data visualisation.
Web

Valentine Sella 2026

Interactive web experience — playful frontend design with CSS animations and micro-interactions.
Web

SYNRGY Academy

BCA scholarship capstone — full-stack web project from the iOS Engineering & Full-Stack Web program.
Let’s talk

Have a hard problem on iOS? Let’s build it.

Open to engineering-leadership conversations, iOS architecture, and fintech product work.

fitrajayaprawira@gmail.com WhatsApp · +62 812-9866-0983 LinkedIn GitHub