Jaydeep Agravat
Resume
Now learning German fintech: SEPA Instant, PSD2, BaFin

I build mobile apps people depend on.

React Native engineer. I'm the only mobile engineer on a live quick-commerce app with 50K+ downloads: I rebuilt its customer app, maintain its rider app, and own every release on Android and iOS.

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Jaydeep Agravat
Gujarat, India
Open to remote or relocation
50K+
downloads on the app I own
11
store releases in four months
99.87%
crash-free users
17
apps live on the Play Store and App Store

01 Now · Zaster

Learning German fintech by building a payment app

Zaster lets a student pay at a café counter phone to phone, straight from one bank account to another over SEPA Instant: no card, no terminal, no fee. I built it to learn how euros really move between banks, what German law asks of a till and a receipt, and how a payment app makes sure nobody ever pays twice.

See the codeRead the handbook →
A payment in six steps: the café rings up €6.30, a one-time QR code appears, the student scans it, confirms with a PIN, sees Paid, and the café's till turns green.
Wallet app (React Native)Till app (React Native)Web dashboard (Next.js)Support consoleFastify + Postgres ledger
  1. 01

    The lost answer

    The bank moved the money, but the café Wi-Fi dropped before the phone heard back. The app shows Checking instead of guessing, and an idempotency key makes sure it is charged once.

  2. 02

    Every cent adds up

    A double-entry ledger, with the rules enforced inside the database, so balances always add up.

  3. 03

    You can't hotfix a phone

    Kill switches, plan features and the oldest supported app version live on the server and change within a second.

  4. 04

    Germany's rules

    Receipts that can't be edited (GoBD), a DATEV export, and GDPR deletion that keeps the 10-year payment records.

What I'm studying alongside it

Payment rails
SEPA Instant (SCT Inst)Instant Payments RegulationVerification of PayeeEPC QR codes
Regulation
PSD2 and SCABaFin licensing (ZAG, EMI)GDPR / DSGVO
Tills and tax
KassenSichV and TSEGoBDDATEV
The market
girocard and cashWero and EPIN26, Trade Republic

02 Case study · Diarch Group · Jun 2026 – Present

DiarchGo: owning a live quick-commerce app

DiarchGo is a live quick-commerce delivery service with 50K+ downloads, fulfilling orders every day from its own network of dark stores. I own both of its mobile apps, customer and rider, on Android and iOS.

  1. 11
    store releases in four months
    99.87%
    crash-free users

    Only mobile engineer, every release

    I own both apps on Android and iOS. The customer app holds 99.87% crash-free users (Google Play vitals, last 28 days). In the older app I hotfixed a crash on the cart screen and released the fix the same day, and fixed push notifications that were not reaching iOS customers or were arriving twice.

  2. 50+
    screens
    1,861→4
    inline styles

    Rebuilt and launched the customer app

    Rebuilt from scratch in React Native 0.86 (New Architecture, Hermes) and strict TypeScript. Server data lives in TanStack Query, app state in 3 small Zustand stores, and a design system with light and dark themes replaced almost every inline style.

  3. 7.7 s→0.3 s
    JS blocking time
    20.8%→6.1%
    dropped frames
    86→0
    re-renders per product card

    Product lists that stay smooth

    I built a small profiling tool, found why memoization was silently failing, and fixed it. Re-renders fell from 86 per product card to none across the same eight-swipe scroll test.

    Measured on the Order Again screen on an iPhone simulator, identical eight-swipe runs.

  4. ₹80K→₹25K
    a month, both apps

    A smaller Google Maps bill

    Calls were repeating needlessly: distance re-fetched on every order update, address on every screen visit. I removed the duplicates and cached results on the device.

  5. 1 click
    from build to store testing

    First CI/CD pipeline, plus OTA updates

    GitHub Actions and Fastlane build, sign and ship to Play Store testing or TestFlight, then promote to production. I added over-the-air (OTA) updates with Stallion so urgent fixes do not wait for store review.

Also built

Checkout and live order tracking

Razorpay with orders created and payments verified on the server, wallet and coupons; rider location in real time over socket.io. Fixed a bug that showed successful payments as failed and invited customers to pay twice.

Lighter assets

Cut bundled images and assets from 10.3 MB to 1.3 MB and the JS bundle from 9.1 MB to 6.9 MB against the old app, with SVG icons, compressed images and a pre-commit check that blocks raw images.

One typed REST client

A single Axios client for every API call: one error format, and an expired login renewed in the background before the request is retried. Audited the APIs with the backend team and documented 14 fixes for slow queries.

Native Android code

Wrote a Kotlin native module that reads the login OTP from SMS and fills it in automatically (Android SMS Retriever API).

Rider app flows

Built the return-pickup and exchange delivery flows in the rider app.

  • React Native 0.86
  • New Architecture
  • Hermes
  • TypeScript
  • TanStack Query
  • Zustand
  • GitHub Actions
  • Fastlane
  • Stallion OTA
  • Razorpay
  • socket.io
  • Kotlin

03 My own products

Apps I design, build and run myself

Each one starts from hundreds of real user complaints, keeps a few clear promises, and proves them with numbers.

Invoice Maker on three phones: the documents inbox, a PDF invoice preview and an estimate signed by the client.

Invoice Maker

Get paid for the work, not for the app.

An offline invoice, estimate and receipt maker for tradespeople, built after reading ~110 critical reviews of the most popular invoice apps. No account and no subscription: pay once. Clients sign on the phone, and the PDF carries a scan-to-pay QR code.

  • React Native 0.87
  • Kotlin Turbo Modules
  • 384 tests
  • 5 languages
Read the story and the code
Score Reader on a tablet showing Bach's Prelude in C with red pencil marks, next to a phone showing the score library.

Score Reader

The next page is already there.

A PDF sheet-music reader for Android tablets, the platform that has no forScore. React Native owns the screens; Kotlin owns everything that has to be instant: PDF rendering, foot-pedal page turns and stylus ink.

  • 20 ms pedal page turn
  • 86 ms to open a 100 MB score
  • 14 ms search across 5,213 scores
Read the story and the code

The App Teardown Handbook

How to work out the design of any mobile app without opening its code: airplane mode, force-quit, a second device. I tested the method on Bluesky, Expensify and Joplin, then checked every conclusion against their source code, and published the ones it got wrong.

Read it online → Code
55
chapters
443
probes anyone can run
53
conclusions confirmed by source code
12
wrong, and published too

04 Experience

2 years of React Native, 17 apps live

Jun 2026 – Present
Remote

React Native Developer · Diarch Group

DiarchGo, a live quick-commerce delivery service with 50K+ downloads, fulfilling orders every day from its own network of dark stores.

  • Own the customer and rider apps on Android and iOS as the only mobile engineer: 11 store releases in four months, 99.87% crash-free users.
  • Rebuilt the customer app from scratch and launched it: React Native 0.86 (New Architecture, Hermes), strict TypeScript, TanStack Query and Zustand.
  • Cut JS blocking time from 7.7 s to 0.3 s and dropped frames from 20.8% to 6.1% in product lists.
  • Cut the Google Maps bill from ₹80K to ₹25K a month across both apps.
  • Built the first CI/CD pipeline (GitHub Actions, Fastlane) and added OTA updates with Stallion.
Read the case study ↑
Sep 2024 – May 2026
Ahmedabad

React Native Developer · SilverSky Technology

Mobile app agency. Worked on 22 React Native apps for clients; 15 are live, including apps with 100K+ and 50K+ downloads.

  • Bizzmatch (business networking, 10K+ downloads): made the app ~20% smaller by removing unused media and replacing heavy libraries; built live face verification for profile photos (Vision Camera, ML Kit); added 6 languages, including right-to-left Arabic.
  • Eaziquote (quotes and invoices for UK tradespeople): owned the mobile app end to end; added paid subscriptions (RevenueCat), push notifications with deep links and crash reporting (Firebase Crashlytics).
  • Upgraded React Native on three live apps: Ahir Matrimonial (0.73 to 0.84, 50K+ downloads), 5 Keys Communication (0.68 to 0.81) and NoblCard (0.72 to 0.75).
  • Got two apps approved after four store rejections by adding a guest mode that keeps the user's data after sign-up, switching to the Android Photo Picker, and adding search, bookmarks and medical sources.
2020 – 2024
Education

B.E. in Computer Engineering

Gujarat Technological University · CGPA 8.66

05 Projects · SilverSky Technology

Client apps I shipped

22 React Native apps for clients; 15 are live, including apps with 100K+ and 50K+ downloads. Select a cover to see screenshots.

Business networking · 10K+ downloads

Bizzmatch

  • Made the app ~20% smaller by removing unused media and replacing heavy libraries.
  • Built live face verification for profile photos with Vision Camera and ML Kit.
  • Added 6 languages, including right-to-left Arabic.
Play Store App Store

Quotes and invoices for UK tradespeople · Owned end to end

Eaziquote

  • Owned the mobile app from first build to store release.
  • Added paid subscriptions with RevenueCat.
  • Added push notifications with deep links and crash reporting with Firebase Crashlytics.
Play Store App Store

Ahir Matrimonial

Community matrimony · 50K+ downloads

Upgraded React Native 0.73 to 0.84.

Play Store App Store

5 Keys Communication

Communication training for hearing loss

Upgraded React Native 0.68 to 0.81.

Play Store App Store

Sexual Disease and Infections

Health education · 50K+ downloads

Approved after store rejections: guest mode, Android Photo Picker, search, bookmarks and medical sources.

Play Store App Store

Daily Micro Challenges

Daily challenge habit app

Play Store

Art Living

Streaming on mobile, Android TV and Apple TV

Patidar Matrimonial

Community matrimony

Play Store

06 Skills

What I work with

Mobile
React Native (New Architecture, Hermes), TypeScript, JavaScript, React Navigation, Reanimated, FlashList
Performance and debugging
Re-render profiling, List and app-size optimization, Firebase Crashlytics
State management and data
Zustand, Redux Toolkit, TanStack Query (React Query), REST APIs, Axios, socket.io, MMKV
CI/CD and release
Git, GitHub Actions, Fastlane, OTA updates (Stallion), Play Store and App Store releases
Integrations
Razorpay, RevenueCat, Firebase push notifications (FCM), Notifee, Deep links, Google Maps Platform