[design][microservice] The hardest part of microservices is your data

Watch note for The hardest part of microservices is your data


slides:
https://www.slideshare.net/ceposta/the-hardest-part-of-microservices-your-data

• Microservices is about optimizing for SPEED.
• Manage (aka. reduce) dependencies.
• Data is a major dependency.
• Focus on domain models, not data models
• Stick with these conveniences as long as you can.
• A microservice has its own database
• We need to understand something about the data inside our services and the data outside our services
• Thus, we are building a distributed system, thus, beware of 
• network latency, 
• network partition
• Plan for failures.
• Build concepts of time, delay, network, and failures into the design as a first-class citizen
• How do you “read” data and how do you “update” data.
• Separate reads and writes
  (CQRS, Command Query Responsibility Segregation
  refer to: http://vsdmars.blogspot.com/2018/05/design-even-driven-system-pattern.html
• Performance: N+1 Query Problem
• https://secure.phabricator.com/book/phabcontrib/article/n_plus_one/
• Use Batching Queries to fix it!
• Load all your data before iterating through it.
• Detecting the Problem
• If seeing a bunch of similar queries, this often indicates an N+1 query issue(or a similar kind of query batching problem)
• For our reads and writes, we need some "consistency"
• We need reads and writes. But we expect failures. 
• CAP tells us to pick 2: Consistency, Availability, Partition Tolerance
• CAP is a bad way to think about this.
• Consistency model
  https://en.wikipedia.org/wiki/Consistency_model
• What consistency model do you need, depending on what role you’re playing?
• https://www.microsoft.com/en-us/research/wp-content/uploads/2011/10/ConsistencyAndBaseballReport.pdf
• Tool: debezium.io