J.I.PORTFOLIO · MMXXVI
SENIOR MOBILE & SDK ENGINEER
AVAILABLE Q3 '26—:— LAGOS
No. 01  /  Lagos, Nigeria
Six years architecting cross-platform mobile
applications and SDKs for engineers.
FLUTTER · SWIFT · KOTLIN · RN · EXPO · AI‑NATIVE
Plugin author on pub.dev
Merged PRs to PostHog & Stripe
Currently writing CircleBox.

Jeremiah
Israel.

01 / SurfaceProduction
Apps
Full-stack mobile products — shipped to real users, measured in MAU, stress-tested in production.
Shipped to →App StoreGoogle Play
×
02 / LayerMobile
SDKs
Libraries that live inside other developers' pubspec.yaml, Package.swift, and build.gradle.
Built in →FlutterReact NativeKotlinSwift
Now Building
+CircleBox — Native flight-recorder SDK+Peerpay — Fintech SDK across 27 banks+DSAlingo — Pocket DSA gym, 312 alpha learners+Preggy — RAG & Gemini, on-device search+Stripe Identity Flutter Plugin — pub.dev+Deo AI — Wardrobe agent PWA+Open-source contributions to PostHog & Stripe+CircleBox — Native flight-recorder SDK+Peerpay — Fintech SDK across 27 banks+DSAlingo — Pocket DSA gym, 312 alpha learners+Preggy — RAG & Gemini, on-device search+Stripe Identity Flutter Plugin — pub.dev+Deo AI — Wardrobe agent PWA+Open-source contributions to PostHog & Stripe
EST. MMXIX · 6 YRS IN MOBILE
PROCEED
SET IN INSTRUMENT SERIF & PLEX MONO
6Years in mobile
5Platforms shipped
27Banking clients
312+Alpha learners
10K+App users
10+Merged OSS PRs
§ 01

Index

Ten fragments of a working engineer
Contents
01CurrentlyA status report02DispositionOn craft & obsession03Catalogue of WorkFive positions, 2022–present04ApparatusSelected projects & SDKs05SpecificationsThe technical surface06ContributionsOpen-source & merged PRs07ActivityA year of commits08CorrespondenceWhere to find me09ColophonA note on AI authorship
§ 02

Currently

Updated 16 May 2026 Lagos, Nigeria · WAT
In Progress
PRIMARY PROJECT · 2026

CircleBox

— a flight recorder for mobile apps

A high-performance SDK with a 100% native core for iOS, Android, Flutter and React Native. Captures low-level telemetry continuously, flushes atomically at the moment of crash, and ships under 80 KB on the wire.

Surface
iOS · Android · Flutter · RN
Core
Swift / Kotlin
Status
Pre-release
Type
SDK · Library
CO-PROJECT · 2025 → ONGOING

DSAlingo

— pocket DSA, deliberate practice

A mobile-first DSA gym: SM-2 spaced repetition, a skill tree that shows what unlocks next, five interaction modes. 312 alpha learners and a waitlist open. Built offline-first for deliberate, consistent practice.

Users
312+ alpha
Engine
SM-2 routing
Status
Waitlist open
Type
Product · App
Studying
Desktop apps & Flutter on macOS internals.
→ Going deeper, slowly.
Open to
Collaborating on SDKs, devtools, anything that ships as a library.
contact below ↓
§ 03

Disposition

A short essay on what I do all day
An essay

There is something deeply satisfying about writing an abstraction that other developers actually adopt. Good SDK design is an underrated skill — you have to get the ergonomics right, on the first try, because every typo becomes someone else's stack trace at 3 a.m. I spend most of my time thinking about that.

I'm a mobile engineer with six years of experience and a particular obsession with building things other developers use. If it ships as a dependency in someone else's pubspec.yaml, Package.swift, or build.gradle— I'm interested.

“Cross‑platform without the excuses. Flutter for shared logic, Kotlin for Android-specific performance work, idiomatic Swift when iOS needs native behaviour. One solution does not fit everything.”

I build AI products, but not the “added a GPT call to a button” kind. The kind where the intelligence is the product — RAG pipelines that actually retrieve, vector stores that fit in your pocket, agents that know when to be quiet.

Open source is where I keep myself honest. If you've ever had a stranger leave a thoughtful review on your PR at midnight, you know why people do this. I try to be that stranger.

Outside of code: I love God, I love coffee, and I carry the irrational confidence that this time the build will pass on the first try.

¶ Note — English (fluent), Spanish (conversational), Yorùbá (mother tongue). I read about widget rendering pipelines for fun, and I'll happily argue about platform channels at a whiteboard.
§ 04

Catalogue of Work

Five positions 2022 → present
Roles
2025 — NOW

Senior Mobile Engineer

Peerpay Network/Lagos, NG/Fintech SDK

Architect and maintain a cross-platform fintech SDK in native iOS (Swift), Android (Kotlin), Flutter and React Native — distributed to banking applications nationwide. I lead enterprise integrations and optimise the core financial services infrastructure end-to-end.

27
Commercial banking apps shipping the SDK
24 → 7
Weeks of client integration time reduced to days
−45%
Memory footprint after pipeline rework
+15%
SDK response speed
READ
2024 — 25

Android Engineer (contract)

Anywhere Healing/Remote — California, US/Health · BLE

Developed an Android health platform integrating wearable BLE devices for bioresonance therapy. The work was almost entirely under the widgets — low-level Bluetooth optimisation, offline-first sync, and HIPAA-grade data pipelines for real-time biometrics.

+15%
Faster BLE data synchronisation
+20%
Increase in daily active users after refactor
HIPAA
Compliant biometric data handling
READ
2024

Mobile Engineer (contract)

Shearify/Remote — Muscat, Oman/Flutter · AWS Amplify

Led end-to-end development of a stylist booking platform with a small team. Owned the Flutter codebase, the GraphQL surface, and the AWS Amplify infrastructure underneath it. Quiet release, real traction.

+40%
Stylist bookings within first 3 months
−35%
System downtime via GraphQL & infra tuning
99.9%
Crash-free user sessions on Sentry
READ
2023 — 25

Senior Mobile Engineer

Swires Technologies/Lagos, NG/Flutter · Logistics SDK

Promoted from Flutter Engineer to Lead. Built an automobile support platform from zero to 10,000+ users, and the Vendoor / Vendoor Rider logistics SDK — Android & iOS plugin, end-to-end. Pleasant work; the kind that makes you a better library author.

10K+
Users on the automobile support platform
−30%
Response time after REST & query tuning
2
Public SDK plugins (Android & iOS)
READ
2022 — 23

Mobile Engineer

Impresanera/Rivers, NG/Ride-hailing · WebSockets

Spearheaded development of a ride-hailing platform with real-time tracking and a WebSocket-based dispatch system. First role where I really got to mentor — turns out that's the part of senior I like most.

60%
User adoption rate within 6 months
+50%
Ride-request response rate after WS rollout
+25%
Sprint velocity after mentoring program
READ
§ 05

Apparatus

Selected projects & published SDKs
Catalogue
№ 01 · Flagship2026 → ongoing

CircleBox

A high-performance flight recorder for mobile apps.
preview — native ring buffer

100% native core for iOS & Android, with thin Flutter and React Native bindings. Tracks low-level telemetry continuously, flushes atomically at crash time. Designed to feel like having a black box on every device.

SwiftKotlinFlutterRNFFI
In development →
№ 02 · AI2025

Preggy

A pregnancy nutrition assistant, on-device.
preview — RAG pipeline diagram

Mobile RAG: Google Gemini + a VectorDB for high-speed semantic search. Latency-budgeted so questions feel like conversation, not a request.

FlutterGeminiVectorDBRAG
Case study →
№ 03 · AI2025

Deo AI

A wardrobe agent. Suggests outfits, daily.

AI-powered wardrobe management PWA. Combines weather data, your closet, and a personal style model into outfit recommendations you actually wear.

PWACohereSemantic
Live →
№ 04 · SDK2024

Stripe Identity, for Flutter

A production-ready KYC plugin, published to pub.dev.

100% native iOS / Android implementation under a small, ergonomic Dart surface. The kind of plugin where the README is shorter than the API, on purpose.

pub.devSwiftKotlinKYC
pub.dev →
№ 05 · Product2025 → ongoing

DSAlingo

Pocket DSA, deliberate practice. dsalingo.eljoy.tech

A mobile-first DSA gym with SM-2 spaced repetition that knows what's broken, a skill tree that shows what unlocks next, and five interaction modes so you stop grinding the same problem and start understanding it. Built offline-first — the full curriculum and review schedule sync to the device so you can study on a flight with no signal.

312+Alpha learners
5Interaction modes
SM-2Review engine
4Code languages
FlutterReact NativeSM-2Offline-firstDart
Live site →
Interaction modes
01 · MCQMultiple choiceActive
02 · ArrangeOrder the stepsActive
03 · FillFill in the blanksActive
04 · TracePredict the outputActive
05 · CodeFull editor + testsActive
Tracks
FoundationsArrays → GraphsFree
Interview PrepFAANG-grade routingPaid
Rapid RefreshCompressed resurfacingPaid
Changelog (latest)
Apr 2026 · Closed alpha, 312 learners
Mar 2026 · Skill tree v2 — 18 → 28 topics
Feb 2026 · SM-2 routing ships
Jan 2026 · Trace mode added
Dec 2025 · First lesson on device
§ 06

Specifications

The technical surface, itemised
Spec sheet

I. Languages

  • Dart6 yrs
  • Swift5 yrs
  • Kotlin5 yrs
  • TypeScript3 yrs
  • Pythonwriting

II. Frameworks

  • Flutterflagship
  • React Nativeshipped
  • Exposhipped
  • Jetpack Composefluent
  • SwiftUIfluent

III. SDK Distribution

  • pub.devflutter
  • CocoaPodsios
  • Swift Package Managerios
  • Maven / Gradleandroid
  • npm / Expo modulesrn

IV. Native Integration

  • Platform Channelsfluent
  • JNIfluent
  • Dart FFIfluent
  • Swift FFIfluent
  • BLE (Bluetooth LE)shipped

V. AI / ML

  • Google Geminishipped
  • RAG architectureshipped
  • SM-2 algorithmshipped
  • Cohereshipped
  • On-device LLMsstudying

VI. DevOps

  • GitHub Actionsfluent
  • Fastlanefluent
  • EAS Build / Expofluent
  • CI / CD pipelinesfluent
  • Code signingsurvived
§ 07

Contributions

Open source & merged PRs in libraries you've probably installed
Merged
№ 01 · PostHogMERGED

posthog-flutter

Improvements to the official Flutter analytics SDK. Quiet contribution work — the kind where you read a lot of CONTRIBUTING.md and learn someone else's architecture before you touch anything.

github.com/PostHog✓ shipped
№ 02 · StripeMERGED

flutter_stripe

Contributions to Stripe's Flutter SDK. The standard for ergonomic payment libraries; a good place to sharpen the craft of 'does this API feel obvious'.

github.com/flutter-stripe✓ shipped
§ 08

Activity

A year of commits @jeremiahseun · github.com
Heartbeat

52 weeks, in colour.

1,719 contributions in the last year
longest streak 19 days · current streak 4 days
← 12 months ago  ·  today →LessMore
1,719Total commits
42Public repos
14Languages used
98%Active weeks
§ 09

Correspondence

If it ships as a library, I want to hear about it
Reach
seunjeremiah@gmail.com
Phone+234 816 379 1889
BasedLagos, Nigeria · WAT (UTC+1)
GitHub@jeremiahseun
StatusOpen to SDK & devtool collabs
Download CVPDF · 3 pages
Colophon
Designed & engineered with AI

On the making of this document.

This site was designed and built in collaboration with an AI assistant — a deliberate choice, not a disclaimer. The composition, the type system, the marginalia, the rhythm of the sections: all iterated with the model as a peer in the room. The intent is mine; the execution was a conversation.

I work this way because AI is a tool I use professionally — for RAG pipelines, for code review, for the long boring middle of any project. It belongs on the portfolio that describes my work.

Nothing here is generated at you. There are no auto-rendered hero images, no purple-to-pink gradients, no oversized chat bubbles pretending to be a product. Every line of type was chosen, every margin set on purpose.

Type
Instrument Serif (display) Newsreader (reading copy) IBM Plex Mono (labels & UI)
Palette
Warm paper, ink, sienna accent — defined in oklch.
Engine
Next.js · TypeScript · Tailwind · Static export.
Built with
Claude — design partner, pair engineer, ruthless editor.
Author
Jeremiah Israel · Lagos, 2026
Set
16 May MMXXVI · v2.0