ScalaMatsuri blog

This blog is about ScalaMatsuri preparation, and sponsored by Hatena, Inc.

A Remap of ScalaMatsuri 2024

ScalaMatsuri2024 has been terrific. June 7 - June 9, 2024, we held the largest Scala conference in Asia. We really appreciate everyone who is a sponsor, speaker, and attendance.

ScalaMatsuri 2024 was an offline event. I hope you have enjoyed this event.

Almost 200 people, which includes staff and attendees, joined this event.

Day1 session was started from Li Haoyi's talk. There are many sessions, lunchtime and after party. We set up a delectable lunchbox to enjoy events.

To succeed in such a large event, community supports are required. It was a resounding success thanks to all members. While we are sad that ScalaMatsuri 2024 is over, it became one of the nice events.

Blog Campaign

We are looking forward to seeing your thoughts on the blogs about ScalaMatsuri 2024.

When posting your blog and submitting a campaign form, you may get the following.

  • 3000 yen discount for the Next ScalaMatsuri ticket
  • In addition, you have a chance to get ScalaMatsuri 2024 commemorative T-shirts through a lottery.

The campaign form will be announced in the ScalaMatsuri X account.

Please post your blog on X with #ScalaMatsuri tag.


Please fill out a survey for the next event.

The event is over.

We are looking for members to join our chair team and staff to start the next ScalaMatsuri events. If you are interested, please join this community.

ScalaMatsuri2024 was a success thanks to your cooperation. We are looking forward to seeing you again.

Thank you.

Open Mic Conference comes again in ScalaMatsuri 2024!

About Open Mic Conference

ScalaMatsuri usually has Open Mic Conference slots.

An Open mic conference is a participant-driven meeting. The term "unconference" has been applied, or self-applied, to a wide range of gatherings that try to avoid hierarchical aspects of a conventional conference, such as sponsored presentations and top-down organization. Wikipedia

You can take your session from now. Otherwise, you can request sessions from someone who you meet on the day of the event.

Your voices make ScalaMatsuri 2024 more passionate.

Open Mic Conference | ScalaMatsuri 2024

What kind of sessions?

ScalaMatsuri 2023 has following Open Mic Conference sessions.

Open Mic Conference sessions are adopted in the morning meeting. You can bring following voices and share them in it.

  • Since I know about FOO "a bit", may I answer your questions?
  • I want to learn about BAR. Is there anyone who can talk about it?
  • Let's play around BEEF together.
  • Why not discuss BLAH-BLAR?

The best part of the Open Mic Conference is that everyone can create a session, rather than one person having to organize it.

Call for sessions

We will held Open Mic Conference for two days. Before begin, we collect your applications for first day Open Mic Conference.

If you want to give a talk, please submit your idea from following link. Adoptions on Day 1 take place at the morning meeting on Day 1.

Open Mic Conference | ScalaMatsuri 2024

We will be giving away special commemorative original acrylic stands for ScalaMatsuri 2024 Open Mic Conference!

We highly encourage you to participate!

ScalaMatsuri 2024 is coming / Submit your talks! #ScalaMatsuri

Hi, folks who love Scala,

We are happy to announce that ScalaMatsuri 2024 will be held in next spring. Now CFP is open, so please submit your talks.

Current Summary of ScalaMatsuri 2024

ScalaMatsuri is the largest tech conference in Asia, which focuses on Scala. In the past events, speakers and attendances came from all over the world, not only from Japan.

In this event, everyone shared recent information and pieces of knowledge about Scala and communicated with each other. There were 26 sponsors and almost 400 attendances joined in the offline and online spaces.

The following are summaries of ScalaMatsuri 2024.

  • Date: June 7 - June 9, 2024
  • Program & Location
  • Venue: Offline

In 2024, we plan to hold ScalaMatsuri from June 7 to June 9. In the first day, we have Scala Training Day. Then we have Main Conference Sessions and Open Mic Sessions in the remaining days.

Main Sessions are held in Tokyo International Exchange Center. Scala Training Day Location is not decided yet.

Call for Proposals

Now we open your talk submission forms for ScalaMatsuri 2024. In this event, there are 2 kinds of talk slots. One is the main talk slot and another is a small talk slot for beginners. We welcome applications from not only experts with a passion for Scala, but also those whose content is aimed at beginners and those who would like to make a contribution to the Scala community using their experience and insight.

CFP outline is as follows.

CFP Forms

Survey Results for Categories of Sessions You Want to Hear at ScalaMatsuri 2024

We have taken a survey about the categories of sessions you would like to hear about at ScalaMatsuri 2024 in November 2023. Thank you to the many people who responded to the survey!

The following are the top results. Please refer to the results below.

  1. Scala3
  2. Software Design and Architecture
  3. Effect System (Cats Effect / Monix / ZIO / eff etc.)
  4. Functional programming in general and sphere theory
  5. Scala Native
  6. Concurrency

Let's restart the offline ScalaMaturi 2024 together!

The event has continued to be held online since 2020, but will return to an offline format for the first time in four years beginning in FY2024.

This year, as with ScalaMatsuri2023, open mic sessions will be held for two days.

So even if you applied for CFP as a speaker but did not win, you will still have a chance to present at ScalaMatsuri if you attend the event. Please join us at the event.

Just like carrying a portable shrine at a festival, let's get ScalaMatsuri 2024 back on track with all the speakers, participants, and sponsors involved.

ScalaMatsuri 2024 offers you the opportunity to grow, learn, and connect as a member of the Scala community. You can discover new ideas and friends, interact with Scala enthusiasts from around the world, and build a future together.

Please stay tuned for more updates on ScalaMatsuri 2024 through this blog and social networking sites!

ScalaMatsuri 2023 guide: Tips on making the online conference experience 120% better

Hello! This is omiend from the ScalaMatsuri Chair Team.

ScalaMatsuri 2023 is just around the corner, and we've been busy preparing for the event. We are writing this year's edition of the "120% Fun Participant's Guide" to help you enjoy ScalaMatsuri even more.

We hope you will read it and come to ScalaMatsuri 2023, and we look forward to seeing you at ScalaMatsuri 2023!

What is ScalaMatsuri?

ScalaMatsuri is Asia's largest international Scala conference.

We are very pleased to announce that more than 400 people attended the last ScalaMatsuri in 2022. ScalaMatsuri 2023 will mark the 10th anniversary since its predecessor Scala Conference in Japan 2013 was held!

Schedule is set!

The schedule has been set, finally. We have a lot of great talks this year!

This year's ScalaMatsuri will feature a keynote session by Daniel Spiewak, the well-known author of the Cats Effect, who will speak on 'The Case For Effect Systems.' This will be a 40 minutes from 10:20 JST on Day1 (4/15), so don't miss it!

Program - ScalaMatsuri 2023

Event Schedule

ScalaMatsuri 2023 will be held for two days on Saturday, April 15th (JST), which is Friday 14th night in the US, and Sunday, 16th (JST).


Registration is scheduled to begin at 9:30am JST.


The opening session will start at 10:00am JST, so please prepare Zoom or Discord before then.

Satellite Venue & Networking Event!

We are planning an in-person networking event on the first day! Therefore, to make it easier for everyone to attend, we have decided to set up a "Satellite Venue" since it would be difficult for everyone to move around if the event is held only online.

Note: The talks will be broadcasted in Japanese in the venue. (Instructions below on how to get the interpreter audio)

The Satellite Venue will be located at the "Sanjou Kaikan" on the Hongo Campus of the University of Tokyo, and the networking event will also be held there!

The deadline for purchasing Satellite Venue & Networking Event tickets is April 15th, 2023 10:00 JST!

In addition, we are grateful to have Givery as a "Satellite Sponsor" at the Satellite Venue.

Please stop by their booth when you visit the venue!

Sanjou Kaikan
7-3-1 Hongo, Bunkyo-ku, Tokyo (on the Hongo Campus of the University of Tokyo)

Notes regarding the Satellite Venue

Multi-language support at the Satellite Venue

  • At the Satellite Venue, the talks will be broadcasted in Japanese language.
  • Due to the restriction of the venue and the hybrid nature, we cannot use the usual wireless receiver to pick up the interpreter audio.
  • Please bring a device such as a laptop or a smart phone that can run Zoom, with earbuds to listen the English audio, and chargers for them.
  • Be sure to bring your earbuds/headphones.
  • We will have power strips if you need to charge up for the full day of conferencing. See Electricity in Japan.
  • General announcements at the venue will be done in both English and Japanese.
  • If you need any assistance, please come talk to a staff the reception.

Note: Due to our delay in announcing the broadcasting language, we'll accept cancellation/refund of Satellite Venue ticket via Doorkeeper.

Food at the Satellite Venue

Food is not allowed at the Satellite Venue.

Apparently, a bottled beverage is considered ok.

In other words, there will be no boxed lunch (bento box) this year. Please take lunch at the restaurants nearby.

COVID-19 Measures

At the venue, we generally recommend wearing masks, but we will leave up to the individuals to decide whether to wear a mask or not. For instance, MCs and speakers will likely not wear masks, and generally staff will not force you to wear masks.

We are planning to place hand sanitizers for your use.

We will not be taking your temperatures, but we may not accept you at the venue, if you obviously look feverish. If you are not feeling well, please be considerate to others and stay home.

Ticket Information

Tickets are required for both the "Online Venue" and the "Satellite Venue & Networking Event" (online registration is free of charge). Please register for the tickets from the link below.

About Sessions

Sessions will be held using Discord + Zoom as usual. Even if you have purchased a Satellite Venue Ticket, Day 2 will be held online, so please prepare Zoom and Discord.

Zoom Webinar

Zoom Webinar is an online video chat service provided by Zoom. It will be used to deliver sessions at ScalaMatsuri.

In a webinar, only the speakers and staff can broadcast video and audio. Participants can enjoy the sessions as viewers with their microphones and cameras turned off.

You will need the "Zoom client for meetings" for Windows or Mac.

If you only have a Linux PC, we recommend watching the Zoom Webinar sessions on a tablet or smartphone.

Download Center - Zoom


Discord is an online communication service that has text and voice chat channels in groups called servers. It will be used as the main venue at ScalaMatsuri for session question-and-answer sessions, chats, and socializing.

Your Discord account name (nickname) and icon will be "your face." You may have a chance to chat with acquaintances you haven't seen in a while, which is common at conferences. To make it easier for your acquaintances to find you, we recommend setting your account name or nickname and icon to something you normally use on social media.

When you click on a voice channel in Discord, you will enter the room with your microphone on. You can turn on your camera after entering the room. To prevent howling, please use a headset or earphones. You can listen to the audio through your speakers while muted.

Please post session questions in the #main-track channel on Discord. The bot will automatically translate between Japanese and English, so you can write in either language regardless of the session language.

For comments and chats during the session other than questions, feel free to post them in the #main-track-chat channel. You can enjoy the conference to the fullest by opening both Zoom Webinar and Discord at the same time. You can download the Discord desktop client from the following link:

Download Discord to Talk, Chat, and Hang Out

Open Mic Conference

We will also be holding an "Open Mic Conference" at ScalaMatsuri 2023. This year, it will be held for the first time separately from the main session for both days.

We plan to prepare many 20-minute presentation slots, so please participate and share your ideas! Details will be announced separately on our blog, so please wait for a while.

ScalaMatsuri 2023 Commemorative T-Shirt

The ScalaMatsuri 2023 Commemorative T-Shirt is now available for purchase at the ScalaMatsuri official online shop! Please take this opportunity to get one and come to the satellite venue!

ScalaMatsuri online shop

Inside is an edition of T-shirts called "Ninja sponsor", and if you purchase it, you can become a Ninja sponsor.

As a benefit of becoming a Ninja sponsor, we will grant you a Ninja role on Discord, so please report it to the staff in the dedicated channel on Discord.

*It takes about one week for the T-shirt to arrive, so please hurry if you want to wear it on the day of the event.

"Ninja sponsor" - ScalaMatsuri online shop

We are sponsored by many companies this year as well!

Please check it out!

Sponsors | The largest international Scala conference in Asia

Code of Conduct

ScalaMatsuri Code of Conduct From the Foreword

ScalaMatsuri is dedicated to providing an open conference for all technologists from various regions and communities. We want to make it a fun experience for everyone, inclusive of gender, race, and many different backgrounds whom they may not meet in their daily life.

The following Code of conduct is a guideline to prevent all of us from making inconsiderate behavior, intentional or otherwise. The ScalaMaturi comittee requires all participants, including speakers and sponsors to comply with the Code of conduct as part of our active step to prevent inappropriate behaviors.

The text of our Code of Conduct also provides an overview of the types of harassment that we define; so please take a look at it.

ScalaMatsuri firmly stands against hateful comments against LGBTQ community as harassment, and will issue citations, warnings, and may remove and/or ban participants from the conference at our sole discretion. In the unlikely event that you say something that could be perceived as harassment, we expect you to retract it immediately, regardless of whether or not you are cautioned by staff.

We appreciate everyone's cooperation in ensuring that we have a respectful and enjoyable time with each other.


ScalaMatsuri is a fun and educational event where you can ignite your passion for Scala and contribute to the development of the Scala community.

Make the most of it and deepen your connections with the Scala community, while expanding your knowledge and experience with Scala!

Thank you!

At ScalaMatsuri 2023, we have decided to hold an Open Mic Conference! This time, it will be held for two days!

Hello. This is omiend from ScalaMatsuri core organizer.

Scala Matsuri 2023 is coming up soon!

We will be holding an Open Mic Conference at ScalaMatsuri 2023!


  • This Open Mic Conference will be held for two days!
  • If you want to give a talk, please submit your idea via this link !
  • The deadline for the first day's CFP is 12:00 PM on April 15th(JST)! You can submit your idea by creating an issue right now!
  • After submit your idea, we will coordinate via Discord, so please make sure to mention your Discord account ID correctly!
  • If you see a session you want to attend on the list (here), give it a thumbs up!

About open mic conference

In short, an open mic conference is the same as what we did as an unconference.

Unconference: A style of conference in which the lecture contents or the speakers are not determined until the day of the conference, and the participants create their own conference by giving a talk on their own. Often the attendees who are interested in giving a talk proposes them during the conference, and the program is determined by the ballot of other attendees.

We wanted to use a more familiar name than "unconference", so we are going with "open mic conference." open mic is defined as:

a session in a club during which anyone is welcome to sing or perform stand-up comedy.

We think this analogy works for the open conference as well.

Open Mic Conference will be held for both days (April 15th and 16th) this year!

Please check the time table for the Open Mic Conference on our GitHub project page:

  • Date: April 15th (14:00 JST) - April 16th (10:00 JST), 2023
  • Time: Each session will be approximately 20 minutes long, but you don't have to use the entire time.
  • The CFP deadline for the first day is April 15th at 12:00 JST.
  • The presentations will be held on Zoom (using regular meeting function, not a Zoom webinar) with a maximum of 100 participants.
  • We are planning to have a satellite venue in a separate room (located underground) with the same format as the main session.
  • We aim to create a relaxed atmosphere that is accessible to everyone. Please keep that in mind.
  • There will be no simultaneous interpretation at the Open Mic Conference. Please use the interpretation bot on Discord.

To apply for a speaking slot at the Open Mic Conference


Please access the following URL:

This will take you to the issue registration screen on the Github repository. Please follow the steps below:

  • Enter the title of your session as the title of the issue.
  • Edit the description according to the content.
  • Submit new issue.

⚠️Please note that if you provide an incorrect Discord account ID, we won't be able to contact you for your presentation request, so please double-check before submitting.


We will select proposals based on the number of 👍 on the issue.

After Selection

Once your proposal is accepted and an issue is created, the details will be shared in a dedicated channel on the ScalaMatsuri 2023 Discord server.

If your proposal is accepted, we will:

  • Confirm your availability to present
  • Conduct CoC check for slide material, if applicable
  • Adjust the time table as necessary

If you want to attend a session in the Open Mic Conference

The link below shows a list of open CFP issues sorted by the number of 👍:

Please feel free to give a 👍 to the sessions you are interested in attending!

Last year's time table had a variety of interesting sessions considering it was an "open mic" format. The sessions included:

An explanation of how to build a safe and flexible always-valid domain model

  • Tips on creating Slides/Scalafix rules
  • Wartremover's Scala 3 compatibility
  • A talk about the big data ecosystem, including Apache Spark and Scio
  • Tips and tricks for using IntelliJ
  • A follow-up to the "Not Just the JVM" talk about Scala's versatility 100 useful features of the Metals tool for Scala development A presentation of the ZIO library app An update on the Scala 3 compatibility of the Play Framework/Twirl A discussion on why understanding and reading code in large repositories can be difficult The second edition of the "Terrible Code Championship" A deep dive into Fibers and how they work A remaining list of items to migrate to Scala 3.

These are the titles that were submitted to the Open Mic Conference at ScalaMatsuri 2022 and have been translated into English.

The category of sessions that participants are interested in for ScalaMatsuri 2023 CFP has been surveyed. As of December 1, 2022, the top categories are:

  • Scala3
  • Software Design and Architecture
  • General Functional Programming and Category Theory
  • Effect System (Cats Effect / Monix / ZIO / eff etc.)
  • Here is the chart with the survey results for your reference:

Please take a look if it helps!

In conclusion

At the Open Mic Conference, anyone can have the opportunity to give a presentation, even at the last minute.

We've had some wonderful sessions presented in the past, but the most important thing is that we believe this is a conference where "anyone can" give a presentation "with ease", and everyone can listen and contribute.

It doesn't matter if your content is small, large, detailed, or rough.

Why not take this opportunity to participate in the Open Mic Conference?

ScalaMatsuri 2023 is just around the corner.

Please take care of yourself and come join us!

Links Open Mic Conference application registration URL for prospective speakers

Open Mic Conference timetable

Open Mic Conference repository

ScalaMatusri 2023

Submit your talks for ScalaMatsuri 2023!

Hi, Ikeda (@taket0ra1) here from the ScalaMatsuri organizer (translated by Eugene).

We're happy to announce the 2023 edition of ScalaMatsuri, the largest Scala event in Asia. ScalaMatsuri is a technical conference about Scala.

We're planning the dates to be April 14 (Fri) EDT / April 15 (Sat) JST and April 15 (Sat) EDT / April 16, 2023 (Sun) JST!

  • Name of the conference
    • ScalaMatsuri 2023
  • Venue
    • Online only
  • Dates (tentative)
    • April 14 (Fri) 9pm EDT, or April 15, 2023 (Sat) 10:00 - 17:00 JST and April 15 (Sat) 9pm EDT, April 16, 2023 (Sun) 10:00 - 17:00 JST (both JST)
  • Talk slots
    • 20 min slot
    • 40 min slot (using two 20 min slots)
      • We'll make 40 min slots available, but generally we're planning to make schedules around 20 min talks.
        • The slot number will likely be finalized depending on the number of submitted talks.
  • Note
    • We've adjusted both the schedule and talk length to suit the online conference.
    • We're considering pre-recording talks for those who might find it difficult to give the talk live due to the timezone. If you wish to pre-record your talk, please let us know in the CFP.

Keynote Presentation

Daniel Spiewak, author of Cats Effect, will give a keynote presentation. Simultaneous interpretation will be provided in Japanese!

Call for Proposal

CFP is open for ScalaMatsuri 2023!

Any topic that might be of interest to Scala learners and Scala community members are welcome, including beginner tutorials, favorite technique, and case studies. As a reference, take a look at last year's schedule for the accepted talks.

To select the talks, we'll run a survey during the early bird ticket sales on what topics people are interested in attending, and the ScalaMatsuri organizers will curate the talks using the result as a reference.

Each year, talk submissions from diverse speakers from all over the world make ScalaMatsuri a great conference. Please consider submitting your talk.

Summary of CFP

  • CPF will close at January 14th (Sat), 2023 Anywhere on Earth (Jan 15th 20:59 JST)
  • Talk length are either 20min or 40min
    • We will mainly accept 20 min talks in ScalaMatsuri 2023
  • Maximum 3 proposals per person
  • We're considering pre-recording talks for those who might find it difficult to give the talk live due to the timezone.
    • If you wish to pre-record your talk, please let us know in the CFP.
  • Talks will be selected by ScalaMatsuri organizers.

Results of the survey on the categories of sessions you would like to hear at ScalaMatsuri 2023

In October, we took a survey on the categories of sessions you would like to hear at ScalaMatsuri 2023 ScalaMatsuri 2023. Thank you for your cooperation.

At this time (December 1, 2022), the top categories are as follows

  • Scala3
  • Software Design and Architecture
  • Functional programming in general and sphere theory
  • Effect System (Cats Effect / Monix / ZIO / eff etc.)

We hope you will find this information useful.

We are also looking for your recommendations for talk sessions!

For the first time, if you have a talk session that has already been presented at a past event that you would like ScalaMatsuri attendees to watch, you can submit it via the CFP Call for Proposals form.

If there are any videos that you think should be shown at ScalaMatsuri, we would like to have the presenter of the video agree to show them at the conference, using the translation function, etc.

  • I am aware of talk sessions presented overseas. I would like to see them spread in Scala Matsuri as well.
  • The content is good regardless of the language, even though it is a talk session for a language other than Scala.
  • There are easy-to-understand videos about the knowledge around licenses.

Please let us know about videos that you think will be useful for the participants in various ways.

Proposal forms

Looking forward to your proposals!

ScalaMatsuri 2022 guide: Tips on making the online conference experience 120% better

Hello, everyone.

This article is written by Irinaka, and translated by OE.

ScalaMatsuri 2022 is just around the corner. Ticket registration is open until the end of day 2, 20th March.

Now, I'm going to show you how to enjoy the online ScalaMatsuri 2022!

TL;DR / Summary

  • Install Zoom and Discord client apps, create a Discord account, and set up your icon beforehand.
  • Prepare a headset or earphones.
  • Check our timetable. We'd encourage you to post your session ideas to Open Mic Conference GitHub repo!
  • Revisit our code of conduct.


For ScalaMatsuri 2022, Day 1 will be the conference day on Saturday, March 19th JST (18-19th EDT/PDT), and Day 2 will be the Open Mic Conference day on Sunday, March 20th JST (19-20th EDT/PDT).

We will use Zoom and Discord throughout these two days.

Read more