Specify an API Request Contract
Check syntax, input contract and authorization before the permitted state change.
About 22 minutes, plus any extended practice
Open lesson 1Design a Reliable Request Workflow
Two increment requests read count 5 and both write 6. Explain the defect, a preservation strategy and a bounded retry policy with delays 1,2,4 seconds.
Before you begin
- Understand server validation, authorization and atomic changes.
Choose by skill rather than age alone. Read with an adult when useful, revisit a lesson, or explore another grade.
Follow the lesson sequence
Distinguish Idempotent Effects from Repeated Events
Compare the intended stored state after one operation with the state after repeating that same operation.
About 22 minutes, plus any extended practice
Open lesson 2Detect a Lost Update in a Concurrent Model
Trace each read and write and compare the final value with the intended combined operation.
About 22 minutes, plus any extended practice
Open lesson 3Bound Retries with a Stated Backoff Budget
Add the listed retry delays and respect the maximum attempt rule.
About 22 minutes, plus any extended practice
Open lesson 4Review and transfer
After the lessons, try 4 new review cases and a practical task. Each answer has an explanation and a link back to the related lesson.
Open the unit reviewGuest answers are temporary. Keep your own paper or document; this unit does not certify completion or record a school grade.
Topic references
- 2026 CSTA PK–12 Computer Science Standards: topic reference — Programming; Systems & Security
These references informed the topic selection. They do not certify complete standards alignment.