The number of unique values in a column in a table.

Mean Time Between Failures experienced by end-users. The higher the time, the more reliable the system.

We make the biggest decisions when we have the least knowledge. Note to myself: Try to chose flexible solutions and be open to adjust them when you know more about the project.

Keep it simple stupid. Note to myself: Most systems work best if they are simple.  Simplicity is a goal. Unnecessary complexity should be avoided.

The term was introduced by Martin Fowler. Build with an intention to rebuild when the time comes. It’s like throw-away prototypes, only in production. When your business grows, you may have to throw away some or all of your previous code base (as eBay did, twice). This does not mean that the previous solutions were Read more…

Mean Time To Recovery measures how long it takes to fix a bug or an outage, either through a rollback or another action. There are also: Mean Time To Repair, Mean Time To Respond, Mean Time to Resolve. Note to myself: The metrics should be as low as possible. Having effective monitoring and alerting systems Read more…

Command Query Responsibility Segregation pattern. This pattern has the following benefits: Supports multiple denormalized views that are scalable and performant Improved separation of concerns = simpler command and query models Necessary in an event sourced architecture and the following drawbacks: Increased complexity Potential code duplication Replication lag/eventually consistent views Note to myself: Try to implement Read more…

It it impossible in a distributed data store to guarantee more than two out of the following three guarantees: Consistency aka every reader receives the most recent write or an error. Availability aka every reader receives a response without the guarantee that it contains the most recent write. Partition tolerance aka a system continues to Read more…