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Leveraging the power of Reactive Architectures Microservices, Reactive and Distributed Systems Vienna Vienna, August 2021

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@duffleit @duffleit [email protected] David Leitner Coding Architect

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Reactive? Programming with, or designing upon, asynchronous data streams.

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asynchronous data streams. Space Time Collections Iterator Generator Value Getter Setter Promise Deferred Resolver Stream Reader Emitter

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The relationship between them is implicit, an idea that only exists in the mind of the programmers. It should be explicit, a part of the language, and existing for all time. Counter and doubled should be bound.

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the Destiny Operator paulstovell.com/reactive-programming

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1 map(x => x*2) 2 3 6 Reactive Programming, is Programming with Streams.

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C’mon, show me a down-to-earth example.

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YAMS — Yet Another Mail Service NEW 2021-04-11 — An important Email 2021-04-09 — Another important Email 2021-04-08 — Do you want to join my network? 2021-04-05 — Nigerian prince wants to send you money X your inbox contains 4 mails 1 NEW Mail Reload Controller Rest Client update UI Element update UI update UI

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YAMS — Yet Another Mail Service NEW 2021-04-11 — An important Email 2021-04-09 — Another important Email 2021-04-08 — Do you want to join my network? 2021-04-05 — Nigerian prince wants to send you money X your inbox contains 4 mails 1 NEW Mail Reload Websocket Client Email Email count() count() collect() filter() subscribe Email map()

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YAMS — Yet Another Mail Service NEW 2021-04-11 — Hello Reactive Systems Vienna! 👋 2021-04-09 — Another important Email 2021-04-08 — Do you want to join my network? 2021-04-05 — Nigerian prince wants to send you money X your inbox contains 5 mails 2 NEW Mail Websocket Client Email Email count() count() collect() filter() subscribe Email NEW 2021-04-11 — An important Email map()

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We move from a pull-based design, to an asynchronous push-based design.

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Reactive Programming Reactive Architectures We take the same concepts from reactive programming and move them up to the system architecture.

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“The Universal BBC Architecture” Back in 2010… Allard Buijze Box Cylinder Box

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Internet has 4.7 Billion users. Facbook has 2.8 Billion users. Youtube has 2.1 Billion users. 2010 2020 The Internet has 1.4 Billion users. A single website may now handle twice as much traffic as the entire internet a decade ago.

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The Reactive Manifesto Message Driven Responsive Elastic Resilient NFR Supported by Enabled by Scalability Extendibility

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Microservice A Microservice B Message Driven Responsive Elastic Resilient Value Form Means

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Microservice A Microservice B Message Driven Responsive Elastic Resilient Value Form Means Microservice B Microservice B

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Microservice A Microservice B Message Driven Responsive Elastic Resilient Value Form Means Microservice B Stream

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Microservice A Microservice B Message Driven Responsive Elastic Resilient Value Form Means requests pile up

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Message Driven Responsive Elastic Resilient Value Form Means Microservice A Stream Microservice B

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We support Back-Pressure Stream Provider Consumer events are stored until consumed Stream Provider Consumer A Consumer C Consumer B scaling out consumers We can horizontally scale by Location Transparency

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We move from a synchronous pull-based architecture, to an asynchronous push-based architecture.

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Push, Pull, Whaaaaaat?

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Microservice A Microservice B Microservice C Web Application

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Microservice A Microservice B Microservice C Web Application Microservice C with high latency First Generation Integrated Synchronous without Backpressure Support

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Microservice A Microservice B Microservice C Web Application Microservice C with high latency Second Generation Partially Asynchronous & Backpressure Support Queue isolates bottleneck Queue

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Web Application Stream Microservice usually Backend-For-Frontend (BFF) Microservice A Microservice B Microservice C Thirds Generation Stream Centric and Fully Asynchronous

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Events as the System State Stream of Transactions Max sent Tim 100€ Max sent Maria 70€ Tim sent Maria 25€ ➡ Current Balance Max - 100€ Tim + 100€ Maria + 70€ - 170€ + 75€ + 95€ Stream-table duality

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Web Application Stream Microservice usually Backend-For-Frontend (BFF) Microservice A Microservice B Microservice C Migration via Change-Data-Capture Legacy Database New User Added User Updated Change-Data-Capture DB Log

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www.squer.link/migration-strategies

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Events as the System State Stream of Transactions Max sent David 100€ Max sent Maria 70€ David sent Maria 25€ Current Balance Max - 100€ David + 100€ Maria + 70€ - 170€ + 75€ + 95€ Stream-table duality the truth, the whole truth, nothing but the truth. Event Souring

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Web Application Stream Microservice usually Backend-For-Frontend (BFF) Microservice A Microservice B Microservice C Thirds Generation Stream Centric and Fully Asynchronous

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Web Application Eventstore Microservice usually Backend-For-Frontend (BFF) Microservice A Microservice B Microservice C Thirds Generation Stream Centric and Fully Asynchronous

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Web Application Eventstore Microservice usually Backend-For-Frontend (BFF) Lambda A Lambda B Lambda C Thirds Generation Stream Centric and Fully Asynchronous

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Web Application Stream Microservice usually Backend-For-Frontend (BFF) Microservice A Microservice B Microservice C Thirds Generation Stream Centric and Fully Asynchronous

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Stream Centric Systems are the only way to build autonomous Microservices.

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by: twitter.com/swardley

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Stream Centric Systems are the only way to build autonomous Microservices.

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Microservice A Microservice B Microservice C UI

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Account Summary Service Transaction Service User Service Web Banking Categorization Service Config Service The rise of the Entity Service Antipattern High Presure Low Resilience Z Y X Payment Service

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Account Summary Journey Transaction Service User Service Web Banking Categorization Service Config Service The rise of the Entity Service Antipattern High Presure Low Resilience Z Y X Payment Journey Paymet Customer Journeys Account Overview Customer Journeys Low service Autonomy Weak Independent Deployability Weak Independent Scalability

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Account Summary Journey Transaction Service User Service Web Banking Categorization Service Config Service Payment Journey projection projection We never write to projections, we only read from them. CQRS in a nutshell websockets Strong Service Autonomy at Runtime Smaller Deployment Footprint Good Horizontal Scalability Account Summary Journey projection

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Lambda A Web Application Lambda B Lambda C Stream GraphQL Microservice A Microservice B Microservice C Web Application ➡ pull-based push-based

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www.squer.at

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Focus on Realtime Integration Insurance Calculation

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GraphQL Step 1 Step 2 Step 2 Car Brand Build Year Car Model Insurance Agent Customer ✅ This Is Correct Alfa Romeo Giulia, 2020 110PS, Diesel Products Users Configurations Eventstore GraphQL car brand has changed Alfa Romeo 2020 Giulia, 110PS

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GraphQL Step 1 Step 2 Step 2 Car Brand Build Year Car Model Insurance Agent Alfa Romoe 2020 Giulia, 110PS Customer ✅ This Is Correct Alfa Romeo Giulia, 2020 110PS, Diesel Step 1 Step 2 Step 2 Coverage 200 € 🏁 Sign Digital Do you accept 70% coverage for 200€? Products Users Configurations Eventstore GraphQL

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GraphQL Step 1 Step 2 Step 2 Car Brand Build Year Car Model Insurance Agent Customer ✅ This Is Correct Alfra Romeo Giulia, 2020 110PS, Diesel Step 1 Step 2 Step 2 Coverage 250 € 🏁 Sign Digital Do you accept 90% coverage for 250€? Products Users Configurations Eventstore GraphQL Customers expect realtime syncronisation between channels.

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Focus on Resilience High Available Banking

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Mobile Banking Usage Show balance & last transactions: 93% Initiate new payment: 3% Any other functionality: 4%

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Transactions Web Banking Users Accounts Stream GraphQL Projection Projections 1⃣ Projections act as read-models for a specific client. 2⃣ They subscribe to events & hydrate the projection. 3⃣ The client only reads from the projection.

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Transactions Web Banking Users Accounts Stream GraphQL Projection Projections 1⃣ Projections act as read-models for a specific client. 2⃣ They subscribe to events & hydrate the projection. 3⃣ The client only reads from the projection. Projection

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GraphQL Mobile Client Projection Transactions Web Banking Users Accounts Stream GraphQL Projection Projections 1⃣ Projections act as read-models for a specific client. 2⃣ They subscribe to events & hydrate the projection. 3⃣ The client only reads from the projection. Only one hard problem in computer science left. 😎 Projection Show balance & last transactions working, 93% of customers still happy. With a concept like optimistic UIs even more.

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lousy memes Ok let‘s sum up! lousy memes within lousy memes High Resilience & Scalability

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Architectural Styles always buy you options. This stuff is cool, Reactive Architectures buy you Resilience, Realtime Capabilities, Elasticity, & Extendibility. you pay by complexity. 💵 e.g. perpetual, or eventual inconsistency

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Maybe start small, and shift to reactive systems once needed.

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by: twitter.com/swardley

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@duffleit @duffleit [email protected] David Leitner Coding Architect squer.at/slides this presentation

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@duffleit