Demo: writing the reviews datastore ADR
On This Lesson 3 topics
This lesson is planned. The outline below lists the topics it will cover. The full lesson has not been published yet.
In this lesson
write an ADR choosing the store for reviews, from evidence. Prepares MID-044-LAB1.
Draft outline details
Step by step
- Context: Shop expects 2 M reviews in a year, 50 writes per minute, reads by product and a rating summary, a flexible optional "attributes" part.
- List options: PostgreSQL (with
jsonb), MongoDB, wide-column. - Score them against the workload and operational cost; include the extra database cost from L03.
- Planned mistake: choose MongoDB because it is "good for reviews", with no numbers. Fix: attach the volume and query evidence; note that 2 M rows with these queries fit PostgreSQL easily.
- Write the decision, consequences, and a revisit trigger (for example "reconsider above 200 M reviews or 5 000 writes/s").
Check your understanding
What must an ADR contain besides the decision?
Show answer
Context, options, consequences, and a revisit trigger.
Practice
Apply this lesson with the module's lab, exercises and quiz.
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