Leo is available for hire
Hire LeoLeo Esaki
Verified Expert in Engineering
Software Developer
Location
Tokyo, Japan
Toptal Member Since
September 27, 2017
Leo is a talented and passionate full-stack developer with a focus on front-end development with React and Angular. He is also strong in building mobile apps with React Native and specializes in dynamic languages such as JavaScript, Python, Ruby, PHP, etc. Leo is passionate about working with motivated teams and getting things done. Currently, he prefers to work with React and Redux. He strictly adheres to the DRY principle and KISS approach.
Portfolio
Chainguard
JavaScript, Hugo, MUI (formerly Material UI), HTML, CSS, React, Go, PWA, WCAG 2...
ScieNFT Limited
Tailwind CSS, Svelte, JavaScript, CSS, Ruby on Rails (RoR), Web3.js...
CoinList Services
React, Ruby on Rails (RoR), Redux-Saga, Redux, Formik, Blockchain, Web3.js...
Experience
Availability
Part-time
Preferred Environment
PyCharm, Git, MacOS, Ubuntu, Visual Studio Code (VS Code), Vercel
The most amazing...
...project I've worked on is a fintech platform that provides a portfolio management solution with intuitive dashboards and a console for clients and advisors.
Work Experience
React and Hugo Developer
2023 - 2023
Chainguard
- Implemented a new documentation site layout using Hugo based on the design provided.
- Implemented a resizable sticky terminal with interact.js.
- Implemented various shortcodes like tabs and cards, etc., for reusability.
Technologies: JavaScript, Hugo, MUI (formerly Material UI), HTML, CSS, React, Go, PWA, WCAG 2, Responsiveness
Front-end Developer
2022 - 2023
ScieNFT Limited
- Implemented a server-side rendering with Svelte-kit.
- Contributed to building an NFT draft editor and profile edit pages with proper field validation.
- Created an infinite scrolling of NFT cards along with a skeleton loader.
- Devised uploading of files with a drag-and-drop feature for creating an NFT.
- Built a mobile responsive UI in the filtering of NFT items.
Technologies: Tailwind CSS, Svelte, JavaScript, CSS, Ruby on Rails (RoR), Web3.js, JavaScript 6, PostCSS, Crypto, TypeScript 3, APIs, Front-end Architecture, Architecture, TypeScript, PWA, CSS Preprocessors, Progressive Web Applications (PWA), DigitalOcean, Responsive, Responsiveness
Front-end Developer
2022 - 2022
CoinList Services
- Involved in maintaining a web market platform built on web3.js.
- Added unit tests to all the front-end UI components.
- Helped to build the internal management tool called "Custody."
Technologies: React, Ruby on Rails (RoR), Redux-Saga, Redux, Formik, Blockchain, Web3.js, User Experience (UX), Web Development, Solidity, Non-fungible Tokens (NFT), Ruby on Rails 4, Databases, Dashboards, User Interface (UI), Single-page Applications (SPA), Agile, REST, Web Applications, Front-end Development, SaaS, NestJS, Auth, Svelte, Fintech, Axios, Cloud Platforms, Web UI, Web UX, Unit Testing, JavaScript 6, Cloud, Trading, TypeScript 3, APIs, TypeScript, PWA, Webpack 4, CSS Preprocessors, Progressive Web Applications (PWA), Bootstrap 4
React Developer
2022 - 2022
Massachusetts Institute of Technology (via Toptal)
- Initiated the front-end project set up with React, Redux, Redux-saga, and Material UI for an open-source data visualization tool.
- Offered large interactive maps with Mapbox GL to navigate to a selected region.
- Implemented chart components for data visualization with VictoryChart and Material UI.
- Implemented a custom smooth scroll navigation with the sticky navbar.
- Rendered GeoJSON data to SVGs with custom area selection using D3.
- Implemented the Small Business Support data visualizations page and comparison page.
- Used Storybook to test all the components in isolation and document them.
Technologies: React, Redux, MUI (formerly Material UI), Mapbox GL, Mapbox API, VictoryChart, Redux-Saga, React Router, D3.js, Storybook, JSX, MERN Stack, Data Visualization, User Interface (UI), HTML UI, Docker, Pixel Perfect, Go, API Integration, Mapbox, Responsive Web Apps, Figma, JSON, JSON Web Tokens (JWT), GUI, User Experience (UX), Web Development, Webpack, Single-page Applications (SPA), Charts, Web Applications, Front-end Development, Google Maps, Axios, Web UI, JavaScript 6, Design Patterns, Azure, APIs, PWA, CSS Preprocessors, Responsive
React Native Cross-platform Mobile App Developer
2020 - 2021
My Roadmap (via Toptal)
- Built pixel-perfect pages using React following the designs given by Adobe XD.
- Updated code layout for better maintenance, particularly for the Redux part.
- Developed a mobile app for iOS and Android, using React Native from React code by using Ionic React and implemented push notifications and deep links.
Technologies: React, Redux, React Native, Django REST Framework, ECMAScript (ES6), Slack, HTML5, JSX, JSON, User Interface (UI), Electron, APIs, PWA, Mobile Development, Android, iOS, Mobile
Senior Full-stack Developer
2020 - 2020
Ready Education (via Toptal)
- Developed several pixel-perfect pages from Figma design using Angular 8 and Tailwind CSS.
- Integrated with phrase.com for internationalization.
- Used NgRx for state management and integrated it with a RESTful API written with Python Flask.
- Performed test-driven development using Jasmine, Karma, and CI/CD with a GitLab pipeline.
Technologies: Flask, Angular, Front-end, Full-stack, CSS, ECMAScript (ES6), Slack, Teamwork, HTML5, JSX, Tailwind CSS, JSON, Back-end, Web Development, Full-stack Development, Single-page Applications (SPA), Web Applications, DB, APIs, AWS Cloud Architecture, Bootstrap 4
Senior React Engineer
2020 - 2020
Defy Gravity Inc. (via Toptal)
- Integrated with Firebase API for efficient data storage.
- Implemented the clipboard functionality of the text editor.
- Applied routing features between chip elements and routes.
Technologies: WebGL, TypeScript, React, Front-end, CSS, ECMAScript (ES6), Slack, Teamwork, HTML5, JSX, User Interface (UI), HTML UI, JSON, Web Development, Single-page Applications (SPA), Web Applications, Internet of Things (IoT), APIs, PWA
React Front-end Engineer
2019 - 2020
Toptal (via Toptal)
- Joined the SEO development team of a Toptal core project.
- Implemented sticky header navigation for the freelance calculator page.
- Worked on optimizing JavaScript bundle sizes for CMS pages.
- Applied the lazy-loading of images to reduce the initial load time.
- Reimplemented the dropdown component to meet the W3C ARIA requirements.
- Fixed the various UI layout issues in more optimized ways.
Technologies: Node.js, Search Engine Optimization (SEO), Server-side Rendering (SSR), React, Ruby on Rails (RoR), HTML, REST APIs, Front-end, CSS, ECMAScript (ES6), Slack, Teamwork, HTML5, JSX, MERN Stack, User Interface (UI), HTML UI, Pixel Perfect, API Integration, Responsive Web Apps, JSON, GUI, User Experience (UX), Web Development, Webpack, SEO Tools, Single-page Applications (SPA), Agile, Web Applications, Front-end Development, NestJS, Web UI, Web UX, Unit Testing, JavaScript 6, TypeScript 3, APIs, PWA, WCAG 2, Responsive, Responsiveness
React Developer
2019 - 2019
Altitude Networks Inc (via Toptal)
- Refactored the file risk management platform to use the latest stacks specific to each version.
- Implemented an API call with cancelable promises using React Hooks.
- Executed the tracking of analytics through Sentry and back-end API calls.
- Reimplemented several UI components based on the new mockups.
- Applied the exporting of large table data as CSV by customizing Griddle.
- Wrote unit tests using Jest and added snapshot tests to all the UI components.
- Built a marketing site including a landing page with Metalsmith site generator.
Technologies: Lodash, Continuous Integration (CI), Sentry, OAuth, Metalsmith, Bootstrap, AWS Amplify, Jest, TypeScript, React, HTML, REST APIs, Front-end, CSS, Functional Programming, ECMAScript (ES6), SSH, ES7, Slack, Teamwork, HTML5, JSX, MERN Stack, Data Visualization, User Interface (UI), HTML UI, Web3.js, Blockchain, Pixel Perfect, API Integration, Responsive Web Apps, Figma, Amazon S3 (AWS S3), JSON, JSON Web Tokens (JWT), Pagination, Testing, JavaScript Testing, GUI, Sass, Web Development, Webpack, Dashboards, Single-page Applications (SPA), Asynchronous Programming, HTML5 Animations, Amazon DynamoDB, Agile, REST, Jira, Web Applications, Front-end Development, SaaS, Auth, CSS3 Animation, Documentation, OAuth 2, Cloud Platforms, UX Design, Web UI, Web UX, Unit Testing, UI Design, JavaScript 6, Cloud, PostCSS, TypeScript 3, APIs, Front-end Architecture, Architecture, PWA, CSS Preprocessors, Responsive, Responsiveness
React Developer
2019 - 2019
Listing Loop Pty Ltd (via Toptal)
- Built an admin management web app for the property listing platform with React and TypeScript.
- Developed the responsive mobile screens of the buyer app for the real estate platform.
- Fixed a slow performance issue with a lagging UI on mobile devices.
- Implemented the pagination with infinite loading for the properties list.
- Handled the implementation of the Firebase DB migration scripts in JavaScript.
- Ensured the components and redux-saga modules were thoroughly tested with Jest.
Technologies: Mapbox GL, Styled-components, Jest, Firebase, React Router, Formik, Redux-Saga, TypeScript, Redux, React, HTML, React Redux, REST APIs, Front-end, CSS, Functional Programming, ECMAScript (ES6), SSH, Slack, Teamwork, Chatbots, HTML5, Next.js, Google Cloud, Google Cloud Platform (GCP), JSX, MongoDB, MERN Stack, User Interface (UI), HTML UI, API Integration, Responsive Web Apps, NoSQL, JSON, JSON Web Tokens (JWT), Pagination, Serverless, Testing, JavaScript Testing, GUI, Web Development, Webpack, Databases, Dashboards, Single-page Applications (SPA), Asynchronous Programming, REST, Jira, Web Applications, Front-end Development, Auth, Google Maps, Axios, Unit Testing, Cloud, APIs, TypeORM, PWA, CSS Preprocessors
Full-stack Engineer
2018 - 2019
Emprove Inc.
- Built back-end APIs with Node.js, Sequelize, Passport.js, etc.
- Built an authentication module and API endpoints for bid management.
- Built front-end UI for the contractor and bid management.
- Implemented AB testing and impersonation features using Google Analytics.
- Implemented a text translation tool for the front and back end.
Technologies: Node.js, React, Redux, Sequelize, Passport.js, React Redux, Elasticsearch, Testing, JavaScript Testing, Amazon CloudFront CDN, Sass, Web Development, Webpack, CI/CD Pipelines, Databases, Full-stack Development, Dashboards, MUI CSS, DevOps, Single-page Applications (SPA), Architecture, Asynchronous Programming, PayPal API, Stripe API, REST, Jira, Back-end Architecture, Web Applications, Auth, Documentation, REST APIs, OAuth 2, Axios, Cloud Platforms, UX Design, Stripe Connect, UI Design, Cloud, DB, PostCSS, Amazon EC2, APIs, Full-stack, TypeORM, PWA, Optimizely, AWS Elastic Beanstalk
Mobile and Web Developer | React Native and AngularJS
2018 - 2019
Lithic
- Contributed to the front-end of the mobile and web apps with React Native and AngularJS.
- Added new screens for the onboarding flow to the mobile app built with React Native.
- Improved the card details screen based on the new mockup.
- Updated the React Native and dependencies version of the legacy mobile app to the current versions.
- Added the new UI pages for the onboarding flow to the web app built on the MEAN stack.
- Improved the card details page based on the new mockup.
Technologies: Pug, AWS SDK, Express.js, Moment.js, AngularJS, MEAN Stack, Redux, React Native, HTML, REST APIs, Front-end, CSS, Slack, Teamwork, iOS, JSX, MongoDB, MERN Stack, Payment APIs, Responsive Web Apps, JSON, JSON Web Tokens (JWT), Web Development, Databases, Dashboards, REST, Web Applications, Twilio, Web & Mobile Applications, APIs, PWA, Mobile Development, Android, Mobile, Mobile Payments, Plaid API
Full-stack Developer
2018 - 2018
Open Polytechnic of New Zealand (via Toptal)
- Refactored the old AngularJS learners dashboard page into Angular 5.
- Implemented the proof of concept feature for learners to set custom course start and end dates.
- Restructured the old integration tests written in Mocha into WDIO (WebDriverIO) tests to run multiple tests simultaneously.
- Handled the portfolio or course model structure migration and refactored the related API endpoints.
- Ensured that multiple reviewers could be added to the courses.
Technologies: Mocha, TypeScript, WebdriverIO, Express.js, Node.js, AngularJS, Angular, HTML, Django, REST APIs, Front-end, CSS, ECMAScript (ES6), Slack, Teamwork, HTML5, JSX, MERN Stack, Less, SQL, Affiliate Programs, JSON, Back-end, Sequelize, Web Development, Webpack, Databases, Full-stack Development, Test-driven Development (TDD), Cypress, Selenium, Web Applications, Axios, Celery, DB, APIs, Full-stack
Full-stack Python Developer
2018 - 2018
S3: Shapiro Settlement Solutions (via Toptal)
- Reimplemented data extraction from the Excel file into various microservice databases based on their new ETL workflow.
- Updated the database models definition in Cloud Datastore, which is used in the new extraction flow.
- Implemented the transformation of imported column data through the front-end UI in React.
- Refactored the back-end APIs to preload entity and relationship options in Python.
- Implemented the UI and back-end APIs for mapping relationships between entities imported from Excel files.
Technologies: Flask, Storybook, GraphQL, Redux, React, Google Cloud Datastore, Microservices, Python, Front-end, Slack, APIs, Teamwork, JSX, SQL, Amazon Web Services (AWS), SQLAlchemy, AWS Lambda, Data Scraping, Microservices Architecture, Amazon S3 (AWS S3), Back-end, Amazon RDS, Web Development, Full-stack Development, Apollo, Pandas, Amazon Simple Email Service (SES), Platform as a Service (PaaS), Celery, DB, MobX, Full-stack
Front-end Web Developer
2018 - 2018
Megawarne Consulting (via Toptal)
- Implemented a new UI layout with Ant Design components.
- Refactored the authentication logic with redux-auth-wrapper.
- Implemented the WebSocket communication between the back end and front end through MessagePack, a binary serialization format.
- Executed showing the field-level validation error message from the back-end API response with redux-form and promise handling.
- Tested and demonstrated React components using Storybook.
- Introduced the HOCs for code reuse, logic, and Bootstrap abstraction.
- Implemented the live detection view through the WebSocket subscription.
Technologies: PostgreSQL, VirtualBox, Apache Maven, Java, Storybook, Ant Design, MessagePack, WebSockets, Redux, React, HTML, React Redux, Front-end, CSS, ECMAScript (ES6), Slack, CSS3, HTML5, JSX, Auth0, JSON, SQLite, Webpack, Web Applications, APIs
Senior UI Developer
2017 - 2017
OpenRisk Technologies LLC (via Toptal)
- Implemented Kafka topics UI into the React and Redux web app to handle real-time data feeds.
- Created a multi-dimensional stocks chart with amCharts.
- Implemented complex diagram visualization and interaction with Ogma.
- Tested and demonstrated React components using Storybook.
- Refactored the authentication logic with redux-auth-wrapper.
- Utilized Immutable.js with PureComponent to boost the performance.
Technologies: Apache Kafka, Storybook, Google Material Design, RxJS, Highcharts, AmCharts, Immutable.js, Redux-Saga, Redux, React, HTML, React Redux, Front-end, CSS, Redux Thunk, ECMAScript (ES6), Koa, Sublime Text 3, Slack, CSS3, HTML5, JSX, Data Visualization, Less, Chart.js, JSON, Charts, Web Applications, APIs, PWA
Shopify Developer
2016 - 2016
Polysleep
- Built an eCommerce platform with Shopify to sell mattresses for stress-free sleep.
- Implemented the customer reviews section by building a custom plugin app.
- Conducted the implementation of multi-language support in English and French with langify.
Technologies: SCSS, Ruby, Shopify, eCommerce, Shopify API, Liquid, Shopify Theme
Full-stack Developer
2016 - 2016
Mosaic Sustainability
- Built a custom CMS to manage micro sites, pages, groups, and users.
- Developed RESTful APIs to connect the Tableau Server and obtain response data.
- Implemented the Tableau view with user-specific settings.
- Involved in building the front end with Angular 2.
Technologies: Tableau, GitHub, Angular, Ruby on Rails (RoR), Vue, Full-stack, Ionic
Full-stack Web Developer
2015 - 2016
Theme Paradise
- Worked on a part-time engagement for the building of several responsive multi-purpose WordPress themes.
- Built my WordPress theme framework called Crystal.
- Implemented WordPress shortcodes for UI components as a WordPress plugin.
- Utilized my strong experience with building WordPress shortcodes along with Visual Composer.
- Implemented a WordPress plugin to handle Ajax calls and reflect the results into the DB.
Technologies: jQuery, JavaScript, WordPress, PHP, Laravel, MySQL, Less, MariaDB, Product Management, Full-stack, PWA, Object-oriented Programming (OOP), WordPress API
Web Developer
2015 - 2016
Nelou
- Built RESTful API endpoints for web and mobile apps.
- Developed cross-browser compliant front ends using AngularJS.
- Tested the front end using Jasmine and the back end using Mocha.
- Implemented the integration with Stripe for card-payment processing.
Technologies: Git, Mocha, Bitbucket, Angular, Ruby on Rails (RoR), PWA
Full-stack Web Developer
2015 - 2015
Charibin
- Developed a fundraising auction system with MeteorJS.
- Improved the UI and UX with Bootstrap based on the mockup provided.
- Revamped the project set up and deployment with iron-cli and mupx.
- Built a module to cache the back-end API responses in the front end to improve performance.
- Conducted technical and functional research and analysis.
Technologies: Google Places API, Bootstrap, Stripe, Meteor, MySQL, Heroku, Jenkins
Web Developer
2012 - 2014
Manglobe, Inc.
- Worked as an internal developer to maintain and upgrade the web app for their internal management system.
- Scripted in Python and Shell for system administration and data processing.
- Led a team of developers, implementing business applications on top of the in-house developed RAD tool.
- Designed and built a real-time chat module using a WebSocket.
- Implemented a continuous integration and deployment process.
- Improved the development and testing workflow with virtualization and container technologies.
- Applied the image recognition engine using OpenCV C++.
Technologies: C++, Python, Ruby on Rails (RoR), .NET, PWA
Experience
Lithic
https://privacy.com/I mostly worked on the front-end side of the mobile and web apps. I added new screens for the onboarding flow to the mobile app built with React Native.
ROLE
• Improved card details screen based on the new mockup.
• Upgraded React Native and its dependencies version of the legacy mobile app to the latest ones.
• Added new UI pages for onboarding flow to the web app built on MEAN stack
• Improved the card details page based on the new mockup.
ROLE
• Improved card details screen based on the new mockup.
• Upgraded React Native and its dependencies version of the legacy mobile app to the latest ones.
• Added new UI pages for onboarding flow to the web app built on MEAN stack
• Improved the card details page based on the new mockup.
Mosaic Tableau Management
- Built a custom CMS to manage microsites, pages, groups, and users.
- Developed RESTful APIs to connect Tableau server and get response data.
- Implemented the view of tableaus with user-specific settings.
- Built front-end with Angular 2.
- Developed RESTful APIs to connect Tableau server and get response data.
- Implemented the view of tableaus with user-specific settings.
- Built front-end with Angular 2.
Nelou CMS
- Developed a RESTful API for web and mobile apps.
- Developed front-end using AngularJS.
- Tested front-end using Jasmine and back-end using Mocha.
- Implemented integration with Stripe for card payment processing.
- Identified and corrected software deficiencies.
- Developed front-end using AngularJS.
- Tested front-end using Jasmine and back-end using Mocha.
- Implemented integration with Stripe for card payment processing.
- Identified and corrected software deficiencies.
Skills
Languages
CSS, CSS3, SQL, Java, GraphQL, JavaScript, C++, C, Sass, HTML5, Python, PHP, ECMAScript (ES6), ES7, TypeScript, HTML, JavaScript 6, Perl, TypeScript 3, Go, Solidity, Less, C#, Ruby, SCSS, Pug, Hugo
Frameworks
CodeIgniter, Bootstrap, Flask, Laravel, Redux, Angular, Django, Ruby on Rails (RoR), React Native, Next.js, MUI (formerly Material UI), Tailwind CSS, .NET, JSON Web Tokens (JWT), MUI CSS, Svelte, .NET Core, ASP.NET, Jest, Django REST Framework, Koa, Express.js, Electron, Ruby on Rails 4, Cypress, Selenium, NestJS, OAuth 2, Spring, Ionic, Ant Design, AngularJS
Libraries/APIs
Highcharts, Vue, REST APIs, Node.js, React Redux, Ramda, Lodash, Redux-Saga, D3.js, jQuery, React, SQLAlchemy, Pandas, PayPal API, Web3.js, Chart.js, Shopify API, Stripe API, Auth, Google Maps, Stripe Connect, Liquid, MobX, WordPress API, Plaid API, Immutable.js, RxJS, Stripe, Google Places API, Formik, React Router, Mapbox GL, AWS Amplify, Moment.js, WebGL, Mapbox API, Passport.js
Tools
Git, GitHub, Bitbucket, Redux Thunk, JSX, Figma, Jenkins, Sequelize, Jira, PostCSS, Optimizely, Webpack, Sublime Text 3, Auth0, JavaScript Testing, Amazon CloudFront CDN, Amazon Simple Email Service (SES), Celery, PyCharm, Mocha, Tableau, Apache Maven, VirtualBox, WebdriverIO, Metalsmith, Sentry, AWS SDK, Slack, Webpack 4
Paradigms
Object-oriented Programming (OOP), Functional Programming, REST, Unit Testing, Mobile Development, Test-driven Development (TDD), Continuous Integration (CI), Testing, Microservices Architecture, DevOps, Asynchronous Programming, Agile, Back-end Architecture, Design Patterns, Responsive, Microservices, MEAN Stack, Search Engine Optimization (SEO), UX Design, UI Design
Platforms
Amazon Web Services (AWS), WordPress, Shopify, Mapbox, Twilio, DigitalOcean, Firebase, iOS, Ubuntu, Windows, MacOS, Blockchain, Docker, Google Cloud Platform (GCP), Heroku, AWS Lambda, Amazon EC2, Azure, Vercel, Android, Mobile, AWS Elastic Beanstalk, Apache Kafka, Meteor, Visual Studio Code (VS Code)
Storage
MySQL, MongoDB, SQLite, PostgreSQL, Microsoft SQL Server, JSON, Databases, Redis, Google Cloud, NoSQL, Amazon S3 (AWS S3), MariaDB, Elasticsearch, Amazon DynamoDB, DB, Google Cloud Datastore
Other
APIs, Full-stack, Front-end, SSH, Web Development, MERN Stack, Data Visualization, API Integration, Responsive Web Apps, Pagination, Full-stack Development, Dashboards, Single-page Applications (SPA), Charts, Web Applications, Front-end Development, Axios, Architecture, Pixel Perfect, PWA, CSS Preprocessors, Bootstrap 4, Storybook, WebSockets, OAuth, Teamwork, Non-fungible Tokens (NFT), Chrome Extensions, SEO Tools, User Interface (UI), HTML UI, Affiliate Programs, Data Scraping, Payment APIs, Back-end, Amazon RDS, GUI, User Experience (UX), CI/CD Pipelines, eCommerce, Product Management, HTML5 Animations, Apollo, SaaS, CSS3 Animation, Fintech, Documentation, Internet of Things (IoT), Cloud Platforms, Platform as a Service (PaaS), Web & Mobile Applications, Shopify Theme, Web UI, Web UX, Crypto, Front-end Architecture, TypeORM, Serverless, Data Structures, AWS Cloud Architecture, Mobile Payments, Progressive Web Applications (PWA), WCAG 2, Responsiveness, AmCharts, Google Material Design, MessagePack, Styled-components, Server-side Rendering (SSR), VictoryChart, Cloud, Trading, Chatbots
Education
2008 - 2012
Bachelor's Degree in Computer Engineering
Tokyo University of Science - Tokyo, Japan