Questions tagged [event-sourcing]

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Event sourcing and sync between write and read model

I am creating this project based on event sourcing and cqrs. My write and read model are on different databases (and machines) and are connected through an event bus (in particular I am using ...
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11 views

Aggregating events [duplicate]

I am in process of designing a service for estimating time of arrivals based on 2 different events. So the service is subscribing to events which in its most simple for looks like: Job (JobId, ...
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5answers
148 views

Effective methodology in designing event driven systems

I understand "the works" of event driven systems and I've built simple ones. However I find that I am struggling a bit in efficiently designing one. E.g., Formulating all the events upfront seems not ...
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1answer
69 views

Decoupling from third party library

I'm doing a project in PHP and I'm implementing Aggregates and Event Sourcing. In order to avoid coding up all the logic related with ES myself I've decided to use a third party library called ...
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1answer
48 views

ActiveMQ for event driven architecture

I am using ActiveMQ and I have a scenario where I need to update the event for 100 consumers parallelly. I am looking for a solution where the 100 consumers receive the event parallelly (i.e there ...
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2answers
115 views

Should microservices in an event sourced architecture not communicate directly with one another via REST/gRPC/etc?

I'm trying to wrap my head around event sourced architectures. It seems like common advice is to have small events with as little info in them as possible (opposed to large events with everything in ...
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1answer
65 views

Event Sourcing, state in events vs state in projections

I would like to ask what is the preferred way of passing additional state to projections. I have UserAggregate that is watching changes of several attributes of user (for instance address, name and ...
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0answers
41 views

Design of Spring boot endpoint that returns large amount of data continously until complete

I'm developing a web application using Spring Boot and React, that needs to return information about hotels from different cities: As an input of the controller, I receive a list of cities that can ...
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2answers
166 views

CQRS - How can a command properly validate when queries are required?

I'm aware that this question has been asked several times, but I have some concerns regarding querying from the write side that I don't see addressed in the already existing questions, more ...
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0answers
37 views

Event sourcing and state set event

I'm trying out commanded framework for Elixir that implements event sourcing and CQRS (it have abstract structure of command, command middleware, router, aggregate, process manager, projection and ...
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2answers
50 views

Event Sourcing - Can a read model/projection be used in business rules within an aggregate?

I know that the general concept behind event sourcing is that the state of the application should be able to be replayed from the event stream. Sometimes, however, we need to get information for ...
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1answer
54 views

Same Event types for multiple micro-services

In an Event Driven Architecture when there are more than one microservices say A, B that publish same Event say Order_Created and a service C listening to it, performs some actions and publishes an ...
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1answer
128 views

What is the correct way to get differences for Event Sourcing (C#)

I am looking into Event Sourcing. One of the key points is about saving the differences to the event store rather than objects themselves. This is fine in simple examples. However, I am struggling ...
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0answers
59 views

Is one to one mapping necessary between Write Applications and Read Applications

Introduction: We have a bunch of micro services (about 40) to serve our customers. To facilitate scaling and audit-ability of selected few micro services we have decided to redesign them using CQRS ...
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1answer
57 views

Event Sourcing Aggregate Roots - Interaction between aggregates and reconstitution

I have been doing a lot of reading/watching on event sourcing but some things still do not quite make sense. My application is a warehouse management system where we have: Deliveries of stock into ...
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2answers
93 views

How to manage event dependencies in event-driven architectures?

I'm trying to design an event-driven architecture based on Kafka for messaging but I'm struggling in managing event dependencies. Let's suppose the following service choreography: Service A: emits A-...
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1answer
211 views

Reducing the code duplication between read and write application in CQRS

I am building an application and trying to embrace Domain Driven design principles, CQRS and event sourcing. We are having two applications one for reading and another for writing. The write ...
1
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1answer
59 views

ES/CQRS: How to access additional information in projections

I'm developing an event-sourced/CQRS application and do not understand the best strategy to use when building the read model projections when additional domain data is needed. A partial representation ...
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1answer
40 views

How specific should administrative compensating events be in a CQRS/ES system?

Are there any best practices around how specific to make events that are generated administratively, say to clean up after one-off operational issues? For example: Say you have a credit card ...
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3answers
208 views

How to deal with UI data requirements in DDD

I'm using DDD and a CQRS/Event Sourcing architecture so my domain logic is separated in a microservice (e.g: command service) and the read side is in another microservice (e.g: query service). We ...
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1answer
83 views

Is it overkill to use event sourced actor model with message queue which send commands from gateway?

The gateway uses Rabbitmq with Masstreansit to send commands to services. Some of services require event sourcing in their internal architecture. Since I need my aggregate states available, and the ...
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0answers
24 views

Confidentiality concerns in including all state+actions crash report

I am working on creating a method to send crash report details for an Office Add-In created with Redux. Because of the way Redux works, it is possible to get the entire application's state as well as ...
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0answers
54 views

Should perform query at the point of time for the event or the actual time when working with CQRS for queue system?

I'm trying to implement CQRS for a queue system where user can join a queue by clicking a button. The system will tell the user if queue is full. When the user click the button, it raised the ...
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1answer
91 views

How to split Aggregate Root that have equal identity?

In DDD, creating smaller aggregates is encouraged where possible, but in a system we are designing we are running into an issue regarding the identity of aggregates. The system evolves around ...
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1answer
160 views

What's the use of event sourcing and asynchronous message queues for sending commands

In short: Out of order commands end up with out of order events, so does the ordering of the events matter in such situations? Since we are uncertain about the order of commands when an asynchronous ...
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2answers
258 views

CQRS sequential numbering of business documents

I am currently building a microservice-based system to learn CQRS/ES, Docker, AMQP and all the other goodies that goes with it. I have never asked a question online before as I am usually pretty good ...
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1answer
137 views

Reduce duplicates in outbox pattern in event driven systems

Trying to implement the outbox pattern for an event driven system. The outbox pattern in a nutshell is a way to ensure system events are sent to the event log/queue/bus at least once (using the term ...
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0answers
55 views

Same events for different aggregates in CQRS?

I'm developing an application using CQRS + ES. Now I have 2 aggregates which are technically almost exactly the same, only they are different concepts in the domain. Therefore I will separate them ...
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1answer
138 views

How to handle Domain Event handlers ordering

Background: we have 2 bounded context: Inventory and Sale application context is Point-of-sale system Scenario: When a Checkout happen on Sale BC, we would like to decrease quantity in Inventory. ...
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2answers
143 views

Is it a bad practice or uncommon to save “Invalid operation attempted” events in an Event Store when doing Event Sourcing?

I have a simple toy project that deals with Banking operations (cash deposit, withdrawals, wire transfers, open and close accounts). I am wondering whether there is something wrong about saving ...
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2answers
533 views

“event sourcing” vs. “event logging” architecture pattern?

Can event sourcing be considered as the same architecture pattern as event logging? Right now we plan to Kafka (or Kinesis) as a pub/sub persistent event data store. We shall not be implementing any ...
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1answer
155 views

Command Waiting On Event Sourcing Micro-services

I'm very new to micro-services but am trying to learn, so apologies for any ignorance or incorrect information. I have been looking at event-sourcing architecture for microservices and I have a ...
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2answers
117 views

F# DDD Bank Modelisation: Aggregate Design for Event Sourcing

I am designing a toy project dealing with the bank account management in F# with Event Sourcing. I would like to get a bit of review (not really a code review) about my Commands and Events to see if ...
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0answers
49 views

Event Sourcing & Redis

I'm using StackExchange.Redis library, it seems perfect. Hard-coded events related BankAccount with ID 1: // UNSORTED COLLECTION public static List<Event> DomainEvents = new List<Event>()...
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1answer
70 views

Why shouldn't an event pertain to multiple aggregates?

In my experience, it is often said that in event sourcing "an event must belong to one aggregate" and also "an aggregate is your biggest transactional boundary". Why is this? What harm would come of ...
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1answer
49 views

Where to store side effect state in an event sourcing system

I also had a look at How do I deal with side effects in Event Sourcing? but the solution wasn't clear to me. If I store "EmailSent" event in the event stream, I might issue the external request to ...
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3answers
342 views

Event sourcing: event's data (payload) vs metadata

There is often introduced a concept of using metadata in events. I just would like to understand the difference between data (which is referred to as payload) and metadata. I've read what I could ...
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2answers
77 views

Event sourcing in microservices: separate event stores + system-wide event store?

Say each microservice is using event sourcing which means it has it's own event store, do you typically add another "mother" event store that contains all events from all microservices as a source of ...
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0answers
38 views

Using notifications when communicating between services in an event sourcing architecture?

In the context of web apps, I'm trying to get my head around how an event sourcing architecture communicates to services. First, I thought of services constantly polling the event store, but then, ...
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1answer
61 views

Can Aggregate shared between services?

I am working in an event-sourcing architecture and while creating the aggregates I came to an interesting challenge, disclaimer I'm new to this. I have a UserAggregate encapsulating the logic for ...
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1answer
387 views

DynamoDB - Event Store on AWS

I'm designing an Event Store on AWS and I chose DynamoDB because it seemed the best option. My design seems to be quite good, but I'm facing some issues that I can't solve. The Design Events Events ...
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1answer
204 views

How to maintain consistency on write when using Event Sourcing on a Banking System

We have a system that holds credit balances, and we thought event sourcing would be a good fit. Getting the current balance by reading from an eventually consistent projection works. However, I ...
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1answer
71 views

How to approach to ES/CQRS in serverless cloud?

Let's say I want to use CosmosDB for Event Store, where have single collection for all events. Currently it is not horizontally partitioned, but it is a possibility for future. Now, I need to ...
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0answers
448 views

EventSourcing / CQRS Implementation with ASP.NET Core WebApi and Azure Cosmos DB

I was looking for an easy implementation of the Event Sourcing and CQRS Pattern in ASP.NET Core using Azure Cosmos DB as Event Store. As I couldn't find anything appropriate I decided to write a ...
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3answers
196 views

How to model User behaviour that can be shared between microservices in Event Driven architecture?

I have an Event Sourced system that has 3 micro services (simplified): User management - Registering a user, change password etc User account - manages debiting/crediting of the user account balance ...
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2answers
171 views

CQRS and Transactional Event Sourcing, problem while recreating Read DB

I'll first explain the context of my problem. The backend of my current project is using DDD, CQRS and Event Sourcing as a stack (the read DB being a MongoDB, my write DB being an event store). At ...
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2answers
77 views

How to deal with delayed updates?

I have a microservice-based system that has a product service and a store service. I'm using eventstore to propagate events between microservices, so for example when a product is created, the store ...
2
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1answer
60 views

Would Command Sourcing fit better than Event Sourcing in my case

I have the following case: We register data from sensors. Let's say that it is a value reported every second, for one hour a day. So we have over 3k values. These values are processed to try and ...
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1answer
63 views

Event sourcing access by reference

In an event sourcing architecture, what is the typical pattern for passing information about related objects (aggregates)? For example, in a order processing system, should OrderCreated event (...
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1answer
996 views

Confused about commands, domain events and external events in event sourcing

I'm a little confused about commands role in event sourcing distinction between domain and external events If my understanding is right a command represents an action initiated by an actor in terms ...