ScalaMatsuri blog

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

About open mic conference - ScalaMatsuri 2022

Hello. This is Ikeda from ScalaMatsuri organizer.

Scala Matsuri 2022 is coming up soon!

Now that the program for Day 1 has been released I hope you are looking forward to the conference, but we haven't had chance to introduce you to the open mic conference on Day 2.

In this post, I would like like to go over the following: - What is an "open mic conference" on Day 2? - What kind of sessions are the ScalaMatsuri attendees interested?

About open mic conference

In short, an open mic conference the same as what we have been doing 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 proceedings

The details of open mic conference is described in the website as well

but we've created a GitHub repo to collect session and LT (lightning talk) ideas.

Please submit the idea you would like to facilitate to GitHub issue.

You can start submitting now. When you find an idea that you'd like to attend, please vote using GitHub reactiion. We will conduct "morning session" on the open mic conference day (2022-03-20 10:00 JST), and we will create the program together based on the collected ideas and your voting results.

Time Duration Zoom A Zoom B
10:00 ~ 60min Morning Session
11:00 ~ 15min Break
11:15 ~ 30min Session A Session B
11:45 ~ 30min Session A Session B
12:15 ~ 45min Lunch Break Lunch Break
13:00 ~ 15min Break
13:15 ~ 15min LT1 - A LT1 - B
13:30 ~ 15min LT2 - A LT2 - B
13:45 ~ 15min Break
14:00 ~ 30min Session A Session B
14:30 ~ 30min Session A Session B
15:00 ~ 15min Break
15:15 ~ 30min Session A Session B
15:45 ~ 30min Session A Session B
16:15 ~ 15min Break
16:30 ~ 15min LT3 - A LT3 - B
16:45 ~ 15min LT4 - A LT4 - B

There two types of sessions based on the length: LT (lightning talk, 15min), and 30 min sessions. We have created two kinds to accommodate varying size of the talks. (Note: LT doesn't necessarily take up the entire 15min)

In addition to the normal tracks there will be virtual booths by the sponsors. Please take a look at the schedule to check out some of the contents available during the break time.

Previous program

The following is an excerpt from the Day 2 of the previous conferene:

10/18 ScalaMatsuri 2020 Unconference Timetable · GitHub

  • How is everyone doing with Scala training? Case studies
  • The ultimate Scala in practice: Live coding with Airframe on Scala + Scala.js
  • Rough explanation of a CQRS/Event Sourcing system built with akka-typed
  • Show us your Scalafix rules at work!
  • Horrible Scala Code Championship

These sessions encompassed from round table, tutorial, knowledge sharing, and fun events like 'Horrible Scala Code Championship.'

If you have a prepared talk that's fine, but we welcome half-baked "I can talk about X" or ideas.

If you're interested in facilitating a session or have a talk you would like to give, please submit an issue.

Categories ScalaMatsuri attendees are interested in

We have taken a survey of categories of talks the attendees are interested in, so maybe you could use it as a reference in coming up with ideas for the open mic conference.

The following tally covers 212 respondents who agreed to have their response reused:

  • General functional programming or category theory(45 votes)
  • Software design and architecture(38 votes)
  • Scala3(30 votes)
  • Case studies(19 votes)
  • Effect System (Cats Effect / Monix / ZIO / eff etc.)(19 votes)
  • Big Data / Fast Data / Data Science(17 votes)
  • Intro to Scala(13 votes)
  • DevOps & Tools(7 votes)
  • Organization related (6 votes)
  • Inspirational / Uplifting(1 votes)

As we can see, looks like functional programming (category theory and effect systems), software design and architecture, and Scala 3 seems to be the most popular topics.

In closing

We are approaching ScalaMatsuri, but open mic conference lets you participate at last minute. If you've been interested in giving a talk, please submit an issue at Issue.

Submit your talks for ScalaMatsuri 2022!

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

Save the dates for ScalaMatsuri 2022!

We're happy to announce the 2022 edition of ScalaMatsuri, the largest Scala event in Asia. ScalaMatsuri is a technical conference about Scala. Similar to ScalaMatsuri 2020 that was held last year, ScalaMatsuri 2022 will also be an online-only conference.

We're currently planning the dates tentatively to be March 19th (Sat) and 20th (Sun)!

  • Name of the conference
    • ScalaMatsuri 2022
  • Venue
    • Online only
  • Dates (tentative)
    • March 19, 2022 (Sat) 10:00 - 15:00 and March 20, 2022 (Sun) 10:00 - 15:00 (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.

Call for Proposal

CFP is open for ScalaMatsuri 2022!

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 15th (Sat), 2022 Anywhere on Earth (Jan 16th 20:59 JST)
  • Talk length are either 20min or 40min
    • We will mainly accept 20 min talks in ScalaMatsuri 2022
  • 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.

Proposal forms

Looking forward to your proposals!

ScalaMatsuri 2020 guide: Tips on making the online conference experience 120% better

Hello, everyone.

This is OE (@OE_uia), the ScalaMatsuri chairperson.

ScalaMatsuri 2020 is just around the corner. Ticket registration is open until the last minute.

Now, I'm going to show you how to enjoy the first ever online ScalaMatsuri 2020!

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 Unconference GitHub repo! - Revisit our code of conduct.


For ScalaMatsuri 2020, Day 1 will be the conference day on Saturday, October 17th (JST), and Day 2 will be the unconference day on Sunday, October 18th (JST).

We will use Zoom Webinar and Discord throughout these two days.

Read more

ScalaMatsuri 2020 T-shirt shops open now!

Hi, I'm OE (@OE_uia), the ScalaMatsuri Chairperson.

I'm thrilled to announce ScalaMatsuri 2020 t-shirt shop opens today!

We are opening two stores at BASE and Shopify, to bring our products to participants around the world.

ScalaMatsuri official T- shirt shop ( left: BASE, right: Shopify )

The e-commerce shop will hold only ScalaMatsuri 2020 t-shirts and will CLOSE around the end of 2020.

TL;DR / Summary

  • This time, we are producing and delivering t-shirts on demand. Please choose your favorite color and pattern.
  • If you live in outside of Japan, please use Shopify. It will take 1-2 weeks to arrive depending on where you live.
  • If you live in Japan, we recommend ordering from BASE for quick delivery (usually 1 week to 10 days).


Buy it at ScalaMatsuri Official Online T-Shirt shop @Shopify.

It is available in 7 colors, and the base fabric specification varies depending on the color. The price is around US$21~27, plus an additional shipping fee. You can order the one you want.

They are manufactured in various parts of the world, and depending on where you live, it usually takes about 1-2 weeks for the product to arrive.


Visit ScalaMatsuri Official Online T-Shirt shop @BASE to purchase your t-shirt.

There are 7 colors and 2 types of T-shirts: the standard T-shirt (4300 yen) and the slim T-shirt (3300 yen). Please choose your favorite color and shape for your order. All prices include shipping and handling.


We are not aiming to make this T-shirt for profit, so the selling price is the sum of the manufacturing cost and the sales commission of the e-commerce shop.

Due to the on-demand production and delivery of the T-shirts, the production cost is higher than in typical years, and there are some individual differences.

Also, there may be some glue on the garment. Please wash it before wearing it.

If you want to receive before ScalaMatsuri 2020, we recommend you order by the end of September.

Read more

ScalaMatsuri 2020 will be an online-only conference.

This is a post written by ScalaMatsuri chair Taisuke Oe (@OE_uia).

We would like to inform you that [ScalaMatsuri 2020] (, scheduled on October 17th and 18th, 2020, has been an online-only conference.

See: ScalaMatsuri 2020 is postponed to October 17-18, 2020 - ScalaMatsuri blog

Due to the continuing spread of COVID-19 throughout Japan and all over the world, we have decided that going online is essential to ensure both the safety of participants and social interaction. We hope that all Scala enthusiasts will be able to enjoy this opportunity to interact with each other, since these opportunities for interaction have been greatly reduced in the wake of the corona outbreak.

Considering this will be the first time for ScalaMatsuri to be held online, on August 30th, we'll be holding a pre-ScalaMatsuri ,intended to be also a rehearsal, which is an online Lightning Talks meetup. We'll be accepting applications for both speakers and participants by the end of next week.

Edited on August 7th: Now the event page is published.

Pre-ScalaMatsuri LightningTalks online meetup

ScalaMatsuri 2020 Online Overview

At this time, we plan to use Zoom Webinar (sessions) and Discord (announcements, interactions, booths, and party).

The dates and times will continue to be October 17 and 18, 2020 (Japan time).

We will also be holding a pre-ScalaMatsuri event on Sunday, August 30th, with an online Lightning Talks meetup.

Official ScalaMatsuri online shop

This year's T-shirts will be available on the official ScalaMatsuri online shop, which will be open to the public in August. For the first time, we will have multiple colors of T-shirts available for you to choose from, so we hope you'll be able to buy one in your favorite color and use it to celebrate the event.

We will be shipping to both domestic and international destinations, but due to logistical constraints, the colors and specifications of the items may differ slightly. Thank you in advance for your understanding.

Ticket Price Revisions.

Due to major changes in online logistics, we will no longer be providing food and drinks, and as mentioned earlier, we will also be distributing attendee T-shirts separately in our online shop. We are still working on the details of simultaneous interpretation, but it will be provided during the conference part of Day 1.

Therefore, we have decided to reduce the ticket prices as follows

  • Online Regular Admission: 3,000 yen
  • Online Student Admission: FREE
  • Online 2nd day-only Admission: FREE
  • Online Ninja sponsorship: 15,000 yen

Online tickets are available from Doorkeeper:

We apologize for the inconvenience caused by this major change in the specifications for ticket holders.

Therefore, we are accepting cancellations if you wish, but please notify us by August 15 23:59 AoE (August 16 20:59 JST) using the form below. If there are no cancellations by the deadline, we will refund the difference in price.

Refund for ScalaMatsuri2020 ticket

Speaking Environment for Speakers

As communicated separately, we will be arranging the timetable according to the time zone in which the speakers live. Other confirmation and support for the online speaking environment are provided separately.

Thank you for your cooperation and response to the change in speaking arrangements.

Sponsor Benefits Modification

We have already sent out a separate notice to sponsors about how to offer benefits online.

For those sponsors who have already applied for a booth, we are taking questions, concerns, and consultations with them, especially as the specifications of the permanent booths will change significantly with the transition to virtual booths.

Lastly, I'm sure all of you reading this article have been affected by the corona outbreak in a large or small way. We would like to thank you again for your support of the event.

We look forward to seeing you all online!

ScalaMatsuri 2020 is postponed to October 17-18, 2020

This is a post written by ScalaMatsuri chair Taisuke Oe (@OE_uia), translated by Eugene (@eed3si9n).

Due to the situation of coronavirus disease COVID-19, we are postponing ScalaMatsuri 2020 to October 17th (Saturday) and 18th (Sunday), 2020. I'll go over the details and future outlook in this post.


  • The conference is postponed to October 17th (Saturday) and 18th (Sunday), 2020. Depending on the COVID-19 situation in August, we might to switch this year's edition to an online-only conference.
  • We will accept ticket refund requests until March 31st. Please submit refund request form by March 31st.
  • We are continuing to raise support from personal Ninja Sponsors and corporate sponsorship.


ScalaMatsuri is an annual international conference since 2013 ran by non-profit community organizers as a matsuri (festival) of technologists who love Scala. We consider two major values for hosting ScalaMatsuri.

First is various serendipity at the venue. It provides opportunities for participants to find new technology, new finds through talks and discussions, and meet new people, open source projects, companies, and services.

Second is making chances to distribute knowledge. Speaking at the conference creates an opportunity for the speakers in and out Japan to put their thoughts into a technical presentation (ScalaMatsuri staff provides Japanese subtitles for English slides). This could become a trigger for new technical knowledge to be distributed in the Japanese Scala community, or technical knowledge exchange with the communities overseas.

As a means to efficiently realize those values, we have been renting large event spaces and hosted talks, unconferences, and hackathons as ScalaMatsuri. We think it's essential to provide these spaces for the continual growth of the Scala community worldwide.

However, due to the concern over COVID-19 outbreak, many counties and local governments are requesting to refrain from large-scale events. As a result, companies in and outside of Japan, including our sponsors, are discouraging or prohibiting their employees to attend large gatherings.

Unfortunately expert opinions do not allow for optimism in the trajectory of COVID-19 in May, when we originally scheduled ScalaMatsuri 2020. Even if we could host it in May, we expect many people won't be able to attend, and/or we'd need drastic measures to ensure the safety of participants, which would directly undermine the values we wanted to provide with ScalaMatsuri.

We have considered hosting an online-only conference. We are aware of multiple conferences that have switched to online-only at the last minute and succeeded to some degree. However, given the current ScalaMatsuri resource and our broadcasting knowledge, our call is that two-month preparation might not be enough to host an adequate online conference.

As the result, we determined that the optimum answer for participants, sponsors, speakers, and community would be to postpone ScalaMatsuri 2020 at this point. The postponed dates are October 17th (Saturday) and 18th (Sunday), 2020.

In case the COVID-19 situation does not improve by mid August we are planning to switch this year's edition to an online-only conference. We will prepare for the contingency in parallel. Therefore, we advise participants from overseas not to make travel arrangements until the August announcement.

Minimizing the effect of postponement

ScalaMatsuri is made up of participants, speakers, sponsors, and volunteer staff members who organize the event. We sincerely hope that we can minimize the effect of the conference postponement.

Ticket holders

Some of the ticket holders may not be able to make it to the postponed date. We're sorry that we'll miss you and we would accept refund requests until the end of March, 2020.

If you would like a ticket refund, please submit the refund request form by March 31, 2020. If you can attend on October dates, the ticket will carry through without further actions.

CFP applicants

We apologize for the delay in announcing the speakers. We are determining the acceptance based on the voting results and the recommendations from the selection committee.

We hope to send the acceptance notice in the next 2 weeks. We will confirm with the speaker if they can attend on October 17th and 18th, and will be accepted upon confirmation.

Corporate sponsors

We would like to extend our thanks for supporting ScalaMatsuri.

ScalaMatsuri will provide the same benefits

How to support ScalaMatsuri

We would like to extend our thanks to many who have reached out to support ScalaMatsuri. For individuals, we've created personal Ninja Sponsor; and for corporations we have sponsorships.

Ninja Sponsor

Ninja Sponsor is a sponsorship plan for individuals. You can attend the conference with Ninja Sponsor ticket, and in addition we're planning to create a small token of appreciation for your patronage.

You can apply for Ninja Sponsor from the Doorkeeper page.

It's possible to upgrade a regular ticket to a Ninja Sponsor. In that case, please use the refund request form and cancel the regular ticket.

We also welcome Ninja Sponsor from the speakers.

Corporate sponsorship

If you're interested in corporate sponsorship, please send your inquiry via below form.

ScalaMatsuri inquiry form / 問い合わせフォーム

Future outlook

Even looking back to 8 years of organizing ScalaMatsuri, this is a highly unusual situation that we have never experienced. There remains various uncertainties, and (although we have evaded critical hits) the budgetary burden too is higher than usual.

On the other hand, we stand in a rare situation where we are given extra time to prepare for the conference after the heavy lifting of CFP is over. We hope to use this to improve the conference and to energize the local Scala community.

In particular, in addition to the regular ScalaMatsuri 2020 conference preparation we are planning the following actions:

  • Preparation for online-only conference by October.
  • Planning and organization of a smaller online subevent before October.
  • Call for additional lightning talk speakers.

How to contact us

ScalaMatsuri organizer is available to discuss any questions and concerns by the following contact form.

ScalaMatsuri inquiry form / 問い合わせフォーム


ScalaMatsuri 2020 will be postponed to October 17th (Saturday) and 18th (Sunday), 2020. Depending on the COVID-19 situation in mid August, we might switch to an online-only conference, so we advise participants from overseas not to make travel arrangements yet.

We will accept ticket refunds until the end of March. We hope to send out CFP notices in 2 weeks.

Individual Ninja sponsorship and corporate sponsorship are welcome.

Stay healthy, and thanks for your continued support of ScalaMatsuri!

ScalaMatsuri 2020 tickets registration and ranked voting sessions open now!

Hi there! This is @OE_uia, the ScalaMatsuri chair.


TL;DR. Here are the summary of this post.

  • Tickets are available now on ScalaMatsuri 2020 event page.
  • The voting will be conducted by ticket holders, sponsors, and staff. It will close at Saturday February 22th, 23:59 AoE (Anywhere on Earth).
  • The voting will be ranked voting style this year. The voting UI will be available directly from the ScalaMatsuri website after logging in.

Tickets & registration

ScalaMatsuri 2020 will be a two-day conference, held on Friday May 15th, Saturday May 16th.

  • On Friday May 15th, it holds mainly Conference, which timetable will reflect on your voting!
  • On Saturday May 16th, it holds Unconference and OSS Hackathon.

Today, we've launched the ScalaMatsuri 2020 event page and started the registration of tickets for two days and only second-day.

ScalaMatsuri 2020 - Doorkeeper

Please note that those who've submitted the talks do not have to register for the tickets yet -- if your proposal is accepted, you can participate without tickets.

As always, we thank Doorkeeper for sponsoring event registration system!

How to vote.

Participants who bought a ticket, sponsor companies and ScalaMatsuri staffs are eligible for voting. This article covers how participants can vote. Reception numberss for voting will be provided with Sponsors and ScalaMatsuri staff separately.

1.) Confirm your reception number.

Confirm your e-mail address that you used to buy the ticket, and the reception number in the e-mail you have received from DoorKeeper.

Doorkeeper reception number

The email you have received from Doorkeeper contains the QR code with your reception number (your 6 digits number below the QR code). You will be asked to enter the reception number when you sign in. We will verify this code later to match up with your Google, Twitter, or Github account that you use to sign in.

If you haven't made the purchase yet, there are some tickets available from the following page:

2.) Sign-in on proposal list page.

From the top right of the proposal list page, press the “Sign-in” button and sign in using your Google, Twitter, or GitHub account. (This will pop up an Authorize application dialog). Google Chrome is recommended.

How to SignIn.

When you sign in, please enter the DoorKeeper reception number. This is it for the preparation.

3.) Ranked voting.

You can vote by clicking on the Vote button. The number of votes per person is limited to 5.

How to vote or pin proposals

As we do previous year, we have ranked voting so that you can choose and place in an order up to five proposals. Your order will also be considered to select proposals. Since ranked voting is tolerant for vote splitting so that we could reduce the number of votes per person and make that easier.

You can drag & drop and put in an order proposals as shown below.

How to put in an order proposals.

The voting will close on February 22th 23:59 AoE(Anywhere on Earth). As long as the voting opens, you can change which proposals you vote, or which order you place in. Any votes afterwards will be invalid, so please be sure to vote early.

Timetable announcement.

Timetable will be public in early March, while we send the results to each candidates who submitted their proposals at the end of February or the beginning of March.

Timetable will be determined by not only voting results but a board of program committee.

Voting FAQ

Q.)How will the voting result be announced?

A.)We will announce the result at the ScalaMatsuri website. We will also announce on the Twitter, so this might a good chance to start following us.

Q.)Is there any extra chance to talk what if my proposal is not accepted?

A.)You can propose your talk for our Unconference, which will be held on the second day of the conference (May 16th). The talks are proposed and assigned on the day of the Unconference in the morning. We tend to have more sessions during the Unconference, so please bring your talks. We will also have Lightning talk sessions, which details will be announced separately.

Please remember to vote!