Muhammed Zain Sajjad, Developer in Karachi, Sindh, Pakistan
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Muhammed Zain Sajjad

Verified Expert  in Engineering

Front-end Developer

Location
Karachi, Sindh, Pakistan
Toptal Member Since
October 13, 2021

Zain is a creative and self-driven full-stack engineer with 8+ years of experience developing and maintaining apps used by millions of people. He focuses on the front end and has ample experience in writing and architecting large-scale, well-tested, and maintained apps. His favorite tools for building scalable apps are TypeScript, Node.js, React, and React Native. Zain has worked with startups and enterprises and managed teams of smart developers to produce out-of-the-box results.

Portfolio

Aroll
Mobile Development, Minimum Viable Product (MVP), Flutter, React Native, Videos...
Monit
TypeScript, NestJS, MySQL, PostgreSQL, REST, RabbitMQ, Apache Kafka...
EFU Life Assurance
NestJS, React Native, Apple Watch, Google Fit, Firebase, Wearables, MySQL...

Experience

Availability

Full-time

Preferred Environment

React, React Native, Node.js, MySQL, TypeScript, Mobile Apps, Redux, REST APIs, Team Leadership, Jest

The most amazing...

...things I've developed are libraries used in apps of several commercial banks used by millions and websites with millions of daily page views.

Work Experience

Node.js/React Native Developer

2023 - PRESENT
Aroll
  • Developed a Tiktok-style mobile app for recruitment in the restaurant and lifestyle industry.
  • Built the back end using Node.js and MySQL and the mobile app using React Native.
  • Completed the launch of the MVP from the idea infancy phase.
Technologies: Mobile Development, Minimum Viable Product (MVP), Flutter, React Native, Videos, Startups, Lean Startups, Firebase, Cloud Firestore, iOS, Android, Full-stack, Location Tracking, Geolocation

Back-end Tech Lead

2021 - PRESENT
Monit
  • Architected and developed a system to manage and track 1000+ devices simultaneously. The system can handle thousands of requests in parallel and scale on demand.
  • Delivered state-of-the-art scalable back end to support thousands of requests coming from GPS, MDVR, and other IoT devices.
  • Managed a team of 10+ developers with a keen focus on architectural improvement and automation to continuously increase the team's productivity. Established learning and growth-oriented cultures in the team for higher retention and better synergy.
  • Involved in planning product direction with stakeholders based on industry trends and client requirements.
  • Worked closely with sales and pre-sales to understand customers' pain points and plan product paths accordingly.
  • Collaborated with other C-level stakeholders in product to develop company roadmap and translate business decisions into technical requirements.
Technologies: TypeScript, NestJS, MySQL, PostgreSQL, REST, RabbitMQ, Apache Kafka, Microservices, Team Management, Agile, Next.js, Material UI, Amazon Web Services (AWS), Vercel, Software Architecture, Automation, Architecture, System Architecture, HTML, JSX, CSS, Software Design, Web Development, Leadership, Scalable Application, Requirements Analysis, Scalable Architecture, Full-stack, SQL, Jira, Technical Leadership, Front-end, Front-end Architecture, Front-end Development, Charts, Data Visualization, D3.js, MongoDB, Express.js, CQRS, Swagger, Design Systems, Mobile Development, CTO, Project Management, Firebase Realtime Database, Payment Gateways, Scrum, GitHub, DevOps, Push Notifications, Location Tracking, Geolocation

Senior Technical Consultant and Architect

2018 - PRESENT
EFU Life Assurance
  • Architected and developed apps for customers to manage their policies and interact with services.
  • Worked closely with business and sales teams to create products that drive results for the organization in terms of retention and new customer acquisition.
  • Oversaw the app growth from an idea to thousands of active users and millions of interactions per month.
  • Integrated wearable and health tracking libraries in-app to increase user engagement.
  • Developed loyalty and rewards app and management system to distribute vouchers and rewards to users.
Technologies: NestJS, React Native, Apple Watch, Google Fit, Firebase, Wearables, MySQL, RabbitMQ, Analytics, CI/CD Pipelines, GitLab CI/CD, React, Next.js, Material UI, Software Architecture, Automation, Redux, Redux RTK, Unit Testing, HTML, JSX, CSS, Architecture, Software Design, Web Development, Leadership, Scalable Application, Requirements Analysis, Scalable Architecture, Full-stack, Mobile, SQL, Jira, Technical Leadership, Front-end, Front-end Architecture, Front-end Development, Data Visualization, D3.js, Swagger, Storybook, Design Systems, Mobile Development, Project Management, Firebase Realtime Database, Payment APIs, Payment Gateways, Scrum, GitHub, DevOps, Push Notifications, Location Tracking, Geolocation

Head of Product

2015 - PRESENT
Peekaboo Guru | FetchSky
  • Played a pivotal role on the team that brought this idea to life, starting from the first day of the development journey until today, when we have millions of active users.
  • Focused on automation and a streamlined CI/CD across our product suite. We worked closely with the QA team to move all our testing to Detox and Cypress. In combination, these increased team productivity and product quality.
  • Designed and built the architecture with a major focus on code reusability across different modules of the product suite. We developed practices and constraints that enabled the codebase to scale easily for a large number of developers.
  • Architected and developed Peekaboo Connect for mobile and a web SDK powering experiences in apps of several commercial banks in Pakistan along with mobile wallets and telecoms. Developed the mobile SDK using React Native and shipped it via S3.
  • Included many mobile machine learning features in our products and developed Guru Eyes, which mimicked geolocated augmented reality using trigonometric formulas and animations.
Technologies: JavaScript, Node.js, React, React Native, MySQL, Elasticsearch, Firebase, Google Analytics, Facebook Pixel, Product Management, Engineering Management, Amazon Web Services (AWS), Redux-Saga, Redux, Redux RTK, Unit Testing, HTML, JSX, CSS, GitLab CI/CD, CI/CD Pipelines, Styled-components, Apache Kafka, Analytics, Agile, REST APIs, APIs, Architecture, Software Design, Web Development, Leadership, Scalable Application, Requirements Analysis, Scalable Architecture, Full-stack, Mobile, SQL, Jira, Technical Leadership, Front-end, Front-end Architecture, Front-end Development, Charts, Data Visualization, D3.js, MongoDB, Express.js, CQRS, Swagger, Storybook, Design Systems, Mobile Development, CTO, Project Management, Firebase Realtime Database, Payment APIs, Payment Gateways, Scrum, GitHub, DevOps, Push Notifications, Location Tracking, Geolocation

Back-end Tech Lead

2023 - 2023
Straight Up Studios
  • Completed the discovery phase of a new multimedia platform that allows users to watch streams from multiple angles simultaneously.
  • Designed a microservices-based architecture for product scalability and quality, focusing on high availability, especially during critical hours of huge traffic.
  • Delivered a project plan for three phases of the product to get cost and effort estimations.
  • Documented and clarified the client's requirements to translate them into a system architecture.
  • Predicted the expected budget for cloud infrastructure based on the number of users as the system scaled.
  • Presented the product development plan to all stakeholders at the end of the discovery phase.
Technologies: Architecture, System Design, AWS IoT, Geolocation

Senior React Native Developer

2022 - 2022
REAL.app, Inc.
  • Established a CI/CD pipeline that enabled publishing iOS and web apps simultaneously using GitHub Actions and fastlane. Saved hundreds of hours of developers' time, resulting in significant improvement in the team's productivity.
  • Established a release management flow with automated changelog generation using GitHub Actions, release-it, and changelog tools.
  • Established commit practices in the team for a more readable commit history using commitlint and Husky.
  • Developed a TikTok-style feed of posts using an optimized implementation of the feed.
  • Built TypeScript patterns for the team to ensure scalability in the codebase.
Technologies: React Native, iOS, Redux-Saga, GraphQL, CI/CD Pipelines, GitHub Actions, Fastlane, JSX, CSS, Web Development, Mobile, Front-end, Front-end Architecture, Front-end Development, Storybook, Mobile Development, Scrum, GitHub, DevOps

Senior Front-end Engineer

2021 - 2022
Freenome Holdings
  • Migrated legacy codebase to TypeScript, increasing the productivity of developers in the team by many folds.
  • Participated in upgrading a major app from old architecture to a more scalable architecture based on MobX and server-side rendering.
  • Migrated from Enzyme to React Testing Library for writing more scalable behavior-driven tests.
  • Maintained docs related to patterns in TypeScript for the current and future team members' learning.
Technologies: TypeScript, React, Jest, Material UI, Testing, MobX, JavaScript, React Testing Library, Enzyme, RTL, Technical Writing, Unit Testing, HTML, JSX, CSS, Web Development, Jira, Front-end, Front-end Architecture, Front-end Development, D3.js, Swagger, Storybook, Scrum, GitHub, DevOps

Front-end Tech Lead

2019 - 2022
Bogo Pakistan
  • Architected and developed mobile app, web app, and marketing website with scalability and automation as core principles that resulted in the completion of product scope in record time.
  • Collaborated with marketing and business teams to integrate tools to analyze user behaviors that helped grow the user base from thousands to over a million.
  • Managed to increase the conversion rate of the new app from 20% to 65%.
  • Developed on-demand Next.js page regeneration using Redis and Vercel APIs to produce the most optimized static site.
  • Created back-end portal with in-depth analysis for business and partners using Recharts and Ant Design.
  • Integrated in-app web view for food delivery websites using encrypted and secure post-messaging-based communication between host and web.
  • Implemented local payment gateways and Checkout.com for transactions.
  • Streamlined automation across the teams for fast delivery and product scalability.
Technologies: TypeScript, React, React Native, Next.js, Redux, React Query, Mobile Apps, User Interface (UI), User Experience (UX), Agile, Automated Testing, Jest, Cypress, Detox, Analytics, Facebook Pixel, Firebase, Engineering Management, Vercel, Redis, Recharts, Ant Design, HTML, JSX, CSS, Architecture, Software Design, Web Development, Leadership, Scalable Application, Requirements Analysis, Scalable Architecture, Full-stack, Mobile, SQL, Jira, Technical Leadership, Front-end, Front-end Architecture, Front-end Development, Charts, Data Visualization, D3.js, MongoDB, Express.js, Swagger, Storybook, Design Systems, Mobile Development, CTO, Project Management, Firebase Realtime Database, Payment APIs, Payment Gateways, Scrum, GitHub, DevOps, Push Notifications, Location Tracking, Geolocation

Associate Software Engineer

2014 - 2015
GfK Etilize
  • Served on the team that worked on products for Best Buy, S.P. Richards, Ingram Micro, and other eCommerce giants of North America.
  • Built an analytics portal using Elasticsearch, Logstash, and Kibana.
  • Developed plugins for eCommerce websites to integrate our rich content on their websites.
Technologies: JavaScript, Elasticsearch, Logstash, Kibana, Jakarta Server Pages (JSP), Software Consulting, HTML, JSX, CSS, Web Development, SQL, Jira, Front-end, Front-end Architecture, Front-end Development, Charts, Data Visualization, D3.js, Express.js, CQRS, Payment APIs, Payment Gateways, Scrum, GitHub, Push Notifications, Location Tracking

Peekaboo Guru

https://peekaboo.guru/karachi
A location-based lifestyle app that shows deals and discounts in towns.

I was part of the team from the very beginning and saw the idea grow into a product used by millions. Led the front-end team that developed a B2C application and website serving millions of users.

Bogo Pakistan

http://bogo.pk/
A React Native-based mobile application. I was the architect and team lead for the product revamp to support the features lined up for many years to come. The product suite includes a public app, a customized library for businesses to add their apps, a back office for the business team, dashboards for marketing teams, and a management portal of merchants to manage their listings and check real-time reporting.

Upgrade to TypeScript

https://www.freenome.com/
Freenome is a biotechnology company based in South San Francisco that has pioneered the most comprehensive multi-omics platform for early cancer detection.

I acted as a senior software engineer on the UI team and worked on the upgrade of all UI libraries and applications to TypeScript. The established TypeScript practices and patterns increased the team's productivity. I also planned and upgraded old apps to the new architecture.

Markeza - The Real Estate Search and Scoring Platform

A React-based real estate web and mobile app enabling users to compare commercial real estate based on several scores.

• Developed a scoring engine that sourced data from 10s of APIs
• ElasticSearch based search engine calculating scores on run time using custom code blocks
• Architected a scalable front-end for performance and scalability
• Adopted the micro frontends architecture for faster delivery of financial calculators and analytical dashboards with hundreds of calculations.

Real App | Senior Front-end Engineer

https://real.app/
Real App is a social media app for content creators to make the most of their creativity.

I worked as a senior software engineer in the social media team. I developed a TikTok-style feed of posts using an optimized implementation of the feed. I also built TypeScript patterns for the team to ensure scalability in the codebase. I established commit practices in the team for a more readable commit history. Tools used included commitlint and husky.

I established a release management flow with automated changelog generation. Tools used: GitHub Actions, release-it, and a changelog.

I established a CI/CD pipeline that enabled publishing app iOS and web apps simultaneously. I used GitHub Actions and Fastlane.

EFU Life PlanIT

https://apps.apple.com/pk/app/efu-life-planit/id1007214538
A React Native-based app for the region's leading life insurance company.

The app integrates all the tools required by marketing to monitor the app's usage. End users can use the app to calculate benefits, monitor fund performance, and request legal documents.

As the lead developer, I managed the team for writing middleware and apps that can scale to many users and have more features.

Tech Blogger | LogRocket

https://blog.logrocket.com/author/zainsajjad/
As a freelance writer for LogRocket blogs, I covered the front-end development and testing areas. I also contributed to updating older posts to keep them relevant to new users. The posts reached millions of readers and were featured in several newsletters.

Tech Blogger | ButterCMS

https://buttercms.com/blog/author/zain-sajjad/
I worked as a freelance writer at ButterCMS blogs, covering the areas of front-end development and testing and updating older posts to make them relevant to new users. The posts reached millions of readers and were featured in several newsletters.

Tech Blogger | Semaphore

https://semaphoreci.com/author/zain
Working as a freelance writer for Semaphore blogs, I wrote about React Native development, testing, and CI/CD. The posts reached millions of readers and were featured in several newsletters. I also developed and maintained React Native community sample projects to use Semaphore CI.

EFU Life Wellness App

A React Native app that connects with wearable devices to monitor vital health and fitness indicators and reward users for achieving health goals. The app also helps users find the number of calories in food using advanced AI. Additionally, it enables users to perform exercises better by leveraging Google's pose estimation.

I worked as an architect and tech lead to deliver the product from its ideation phase. I designed a scalable architecture on the back end to serve millions of users and optimized the mobile app to deliver a pleasant aesthetics and state-of-the-art experience.

Peekaboo Connect

https://fetchsky.com/service/peekaboo-connect/
Peekaboo Connect is a collection of multiple plug-n-play modules which digitize different banking products and experiences.

I was the architect and tech lead responsible for building the front end with React Native. We leveraged RN to create a plug-able SDK for mobile apps using advanced features of RN, explicitly developed for large-scale apps like Facebook.

Languages

CSS, JavaScript, HTML, SQL, HTML5, CSS3, Swift, TypeScript, GraphQL

Frameworks

React Native, Next.js, NestJS, Swagger, Cypress, Jest, Ant Design, Express.js, Tailwind CSS, Jakarta Server Pages (JSP), Material UI, Redux, React VR, Flutter

Libraries/APIs

React, Node.js, REST APIs, React Redux, LocalStorage, React-Intl, React Testing Library, Recharts, MobX, Google AdSense, Redux-Saga, D3.js, React Navigation

Tools

Google Analytics, Facebook Pixel, Webpack, JSX, Fastlane, GitLab CI/CD, Jira, GitHub, RabbitMQ, Prisma, Logstash, Kibana, Viro Media

Paradigms

REST, Best Practices, Agile, Automated Testing, Testing, Microservices, Automation, Scalable Application, Requirements Analysis, CQRS, Mobile Development, Scrum, Responsive Web Design (RWD), Unit Testing, DevOps, E2E Testing

Platforms

Firebase, Blogger, Vercel, Mobile, Amazon Web Services (AWS), Android, iOS, Apache Kafka, Apple Watch, Google Cloud Platform (GCP), AWS IoT

Storage

Redis, MySQL, PostgreSQL, MongoDB, Firebase Realtime Database, Elasticsearch, Amazon S3 (AWS S3), Cloud Firestore

Industry Expertise

Project Management

Other

Writing & Editing, Team Management, CI/CD Pipelines, Teamwork, Software Architecture, APIs, Team Leadership, React Query, User Interface (UI), User Experience (UX), Analytics, RTL, Technical Writing, Redux RTK, Architecture, Software Design, Web Development, Leadership, Scalable Architecture, Full-stack, Technical Leadership, Front-end, Front-end Architecture, Front-end Development, App Store Acceptance Process, Payment APIs, Payment Gateways, Push Notifications, Location Tracking, Geolocation, Detox, Engineering Management, Product Management, Software Consulting, Local Notifications, Enzyme, Storybook, Design Systems, CTO, Google BigQuery, Google AdMob, Software Development, Computer Graphics, Mobile Apps, Microfrontends, Data Visualization, Charts, GitHub Actions, Google Fit, Wearables, System Architecture, Blogging, Content Writing, UI Testing, Deployment, Redux Toolkit, WebAssembly, Styled-components, Firebase ML Kit, Computer Vision, Pose Estimation, Artificial Intelligence (AI), Machine Learning, RTK Query, React Native Bridge, SDKs, System Design, Minimum Viable Product (MVP), Videos, Startups, Lean Startups, AI Content Creation

2012 - 2015

Bachelor's Degree in Computer Science

University of Karachi - Karachi, Pakistan

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