This position is closed and is no longer accepting applications.

Core Engineering - Java Developer

PayPay Minato-ku, Tokyo
  • 💴 ¥7M ~ ¥14M annually
  • 🏡 Fully remote (from Japan)
  • 🧪 6+ years experience required
  • 💬 No Japanese required
  • 🌏 Apply from abroad
  • 🧳 Relocate to Japan

About PayPay

PayPay Minato-ku, Tokyo

With over 55 million registered users (as of February 2023), PayPay is the country’s most popular mobile wallet. Half of all of Japan's smartphone users are using it, and more than 2 billion payments made per year.

Key benefits

  • International engineering team
  • Japanese lessons on company time
  • Incredible scale

About the position

The PayPay Core Engineering team is looking for Java developers to work on improving our suite of internal libraries.

PayPay Core Engineering focuses on addressing core technical problems, leading the improvement of development practices at PayPay and supporting our development teams through a suite of internal libraries streamlining technical functions such as database queries, queue management, logging, monitoring, and encryption. A strong candidate for Core Engineering will have a background in Java/Kotlin product development, good understanding of interactions between the application and the infrastructure, and a strong knowledge of inner working of Java and database management systems.


  • Maintaining and implementing new core libraries used by the product development teams - this imposes high requirements on the code quality, test coverage, well designed architecture and everything required to produce high quality libraries
  • Investigating complex performance issues
  • Active participation in improving Java/Kotlin development practices in PayPay - identifying root causes of inefficiencies and technical defects in product development, proposing potential solutions and driving them to the end
  • Constant technical improvement and research of the new technologies and best practices
  • Assist product development teams in the adoption and updates of internal libraries
  • Assist development and infrastructure teams in investigating root causes of complex technical issues


  • 3+ years of product development in Java/Kotlin
  • 6+ years of total development experience
  • Experience working with Kafka, MySQL, ElasticSearch or similar technologies
  • Experience developing and maintaining high-load high-availability scalable systems
  • Experience in application and database performance optimization

Nice to haves

While not specifically required, tell us if you have any of the following.

  • Working knowledge of Gradle and developing Gradle plugins
  • Experience with TiDB
  • Experience implementing and maintaining technical libraries


7 to 14 million JPY annually.

Meet PayPay's Developers

Ashwini leads one of PayPay’s payment sub-teams. She got there by doing something she’s done throughout her career: identifying something she wants to do and asking to do it.

Read her story...
Photo of Yoseph Savianto

iOS Development at PayPay

with Yoseph Savianto

Yoseph joined PayPay after being attracted to their mission of making Japan a cashless society. As an iOS Engineer, he originally joined their iOS feature team, but now works on their platform team, creating an internal SDK for their iOS and Android apps.

Read his story...

Shilei started working on PayPay before it launched, and has seen it grow into a product used by tens of millions of users. He explains how diversity has helped them overcome challenges, and what PayPay is looking for in candidates.

Read his story...
Photo of Adrian Mariadas

Refactoring PayPay’s Android App

with Adrian Mariadas

Adrian came to Japan to join PayPay as an Android Engineer. As the app has grown in scope, refactoring the codebase to ensure development can continue at a rapid pace has been a big part of his job.

Read his story...

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