ScalaMatsuri blog

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

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