Optimizing the query stack of CQRS-layered applications Dino Esposito JetBrains dino.esposito@jetbrains.com @despos facebook.com/naa4e
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Optimizing the query stack of CQRS-layered applications
Dino EspositoJetBrains
[email protected]@despos
facebook.com/naa4e
Drink Eat
QueryCommand
CQRS ≈ Separating Stacks
Domain layer
Presentation layer
Application layer
Infrastructure layer
Canonical
Layered Architecture
Domain layer
Presentation layer
Application layer
Infrastructure layer
Commands Queries
Data
access
+
DTODomain layer Domain layer
CQRS
Layered Architecture
Conceptual model split into separate
models for update and display
Focus on tasks
Build the data model right for the task
Stop god-mode development
Stop wondering if your model is perfect
CQRS
Architectural spinoffs
Presentation layer
VIEWSFORMS
Infrastructure layer
Domain layer
Presentation layer
Application layer
Infrastructure layer
Commands Queries
Data
access
+
DTO
CQRS
Layered Architecture
Infrastructure layer
Synchronous
Every command triggers sync
updates
Asynchronous
Every command triggers async
updates
Scheduled
A job runs periodically and
updates the read storage
On-demand
Updates triggered by
requests (if older enough)
Automatically
up-to-date
Eventually
up-to-date
Controlled
stalenessControlled
up-to-date
CQRS for Plain CRUD Applications
Presentation
&
Application
Presentation
&
Application
YourApp.CommandStack YourApp.ReadStack
Use the code that does the job
Existing code
Existing products
Existing skills
COMMAND stack
Known patterns
Known techniques
Known practices
O/RM of choice
LINQ
Database in use
READ stackUse the code that does the job
SQL queries
Data binding/grids
JSON / OData
CQRS for Rich CRUD Applications
Presentation
&
Application
Presentation
&
Application
YourApp.CommandStack YourApp.ReadStack
COMMAND STACK
Request for action
Log of actions
READ
DATA
STORE
Aggregate ID Data
Aggregate ID Data
Request for data Formatted data
DETAILED VIEW
Logging the list of commands makes any
CRUD an historical CRUD
Logging the list of
commands lets you
keep track of the
latest without
forgetting anything
that happened in
the past.
PS: if you really want to forget … go with plain CRUD.
SELECT relevant business events
FROM System
WHERE TimeStamp BETWEEN Time1 AND Time2
SELECT relevant business events
FROM System
WHERE TimeStamp NEWER THAN Time1
SELECT relevant business events
FROM System
WHERE TimeStamp OLDER THAN Time1
REPLAY EVENTS
REBUILD THE STATECQRS leads to
Business Intelligence
Ubiquitous Language
When the language of the business is
fully replicated in the codebase
Ubiquitous
Language Query stack
public class Database : IDisposable{
private readonly QueryDbContext _db = new QueryDbContext();
public IQueryable<Customer> Customers{
get { return _db.Customers; } }public void Dispose() {
_db.Dispose(); }
}
DEMOWeb API service using OData and domain-friendly
extension methods for LINQ queries
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