AxonIQ Ask Me Anything session - with Steven van Beelen and Milan Savic

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This video is the recording of our Ask Me Anything session from October 5th, hosted by Ben Wilcock. In this session, several guests asked questions regarding anything related to Axon. These questions were being answered by our Lead Developer of Axon Framework Steven van Beelen and Software Engineer of Axon Server Milan Savic.

Timestamps with each corresponding question:
0:00 Introduction of our speakers and explanation of the Ask Me Anything Session format.
3:15 What resources would you recommend for someone who is just getting started on their Axon journey?
6:07 I want to do a query that can answer the following question: What was the state of my thing (entity or aggregate) x minutes/days/months ago? How do I do this with Axon?
9:24 Is it generally a bad practice to do business validation in event handler annotated methods?
10:59 How badly can you mistreat the event log? (e.g. If you delete events from the domain event entity table what problems will that cause?)
13:20 How well does Axon Framework support MongoDB as a token store? What are the limitations?
14:15 Can you use any other caching servers for Axon Framework saga caching apart from Xcache of Jcache? If yes, is there an example of a configuration?
15:38 There is a Kotlin extension out there still in version 0.1.0, are there any plans to create releases of them on a regular basis, and what is the role of the community in driving this extension forwards?
17:24 What is the suggested way to handle a list of commands send from the clients?
22:00 Is your command handler is supposed to contain your business validation logic? If not how do you keep the validation logic of the aggregate in a central location to minimize duplication etc?
25:11 What are the differences between Axon Server and AxonIQ Cloud?
26:58 Is there a guide to migrate to Axon Server from a database like MariaDB?
30:23 In the basic Event Sourcing scenario you have a few steps to be executed. These steps have to be done in one transaction, but in the meantime, if there was a new record in the event store, related to the aggregate, we have to retry. Is this scenario supported by Axon?
34:18 If the saga event handler is thread safe, are the properties that are being updated by different saga event handlers updated in a synchronous manner?
37:08 Is there an example of a custom association resolver?
39:14 Is it common to split the command mode JPA repositories (set-based validation) from the read model JPA repositories?
41:15 What is involved in implementing a new type of data store with Axon Framework?
45:00 How can I publish an event for a particular aggregate, without a command handler?
46:47 What would be the best next steps to bring my serializer closer to the framework? Should it become a public extension?
48:42 What is the most recommended token store? MongoDB or SQL? What are the benefits of both these options?
50:51 On startup, my Spring Boot enabled application creates at least four tables in the primary status source database, how can I create them in a different database?
53:50 Is there a recommended way on how to handle the necessary changes in representational views when a full replay is not possible anymore?
1:00:32 Will deleting old snapshots in Axon Server be a feature in future versions?
1:02:18 What is the recommended way to do integration testing?
1:06:15 Do you have any recommendations for performing a migration from Axon Server 2.4.x to Axon Server 4 on a production database with three years worth of existing data without any downtime?
1:11:40 When I restart the application server, event replay happens. According to the data I have it will take 10 days to perform the replay. What can I do to avoid this?
1:14:06 Do you have any advice on building a multi-context scenario?
1:19:12 When emitting events using query update emitter from a projection/event handler, is it wise to send or emit these events in the same transaction where the entity of interest is persisted?
1:21:27 I am interested in hearing about benchmarks using Axon Server Enterprise edition?
1:23:26 What does the AxonIQ Initiliazr do and how do you use it?
1:25:22 Does Axon have a publication surrounding best practices related to moving from monolithic thinking and development to microservices?
1:27:07 Thanks and outro.



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