Use when a database schema or data-meaning change needs Parallel Change, including expand, migrate, and contract sequencing for column renames, type or data reinterpretation, large-table backfills, relationship-table changes, enum/status transitions, timezone/default changes, and index or uniqueness changes. This should trigger before framework-specific Flyway implementation guidance when deciding whether a migration needs a compatibility window or whether a simpler migration is sufficient. Part
SkillScore86Maintained
Automatic
◆Data Engineer pack
Last verified 8/20/2026
What it changes
Passed 18 of 21 test cases with the skill, and 10 of 21 without it.
Without skill45%
With skill86%
Checks it passed that the model alone missed
Specifies row-count comparison checks prior to contract execution.
Refers implementation to 313-frameworks-spring-db-migrations-flyway.
Refers implementation to 413-frameworks-quarkus-db-migrations-flyway.
and 1 more in the full report
9 fixed10 passed either way3 still failing0 broke
Pass-rate lift
+41 pp
Tokens
+13%
Agent turns
0%
Response time
-16%
Model gemini-3.6-flashMeasured 8/20/2026v119 of 22 cases passed with skill · 21 comparable
Tokens, turns and time describe resource use, not a dollar price.
See it in action
One of 8 test cases the skill fixed. Same model, same prompt, with and without the skill.
1 of 8
Prompt
Our Micronaut microservice is experiencing slow queries on `orders.created_at`. We want to create a non-unique index `idx_orders_created_at` on this existing column. Should we use an expand-migrate-contract strategy or a single migration file, and which framework skill handles implementation?
What was checked, without and with the skill
Checked
Without skill
With skill
Recommends a single forward-only migration for adding the index.
Passed
Passed
Refers implementation to 513-frameworks-micronaut-db-migrations-flyway.
Missed
Passed
case-04 · gemini-3.6-flash · 8/20/2026 · answers are capped and redacted
What's inside
The instructions your model reads when the skill loads.
SKILL.md63 lines2 files
Parallel Change Design
Guide Java Enterprise developers through Parallel Change for database migration scenarios. This is an interactive SKILL.
What is covered in this Skill?
Deciding whether a database migration needs a compatibility window
Sequencing database changes as expand, migrate, and contract deployable steps
Preserving old and new application versions during rollout and rollback windows
Handling column renames, type or data reinterpretation, large backfills, relationship-table changes, and index or uniqueness changes
Explaining tradeoffs such as temporary dual paths, extra migrations, verification effort, and delayed cleanup
Routing framework-specific implementation to Spring Boot, Quarkus, or Micronaut Flyway skills after the design approach is clear
Constraints
Use Parallel Change as a database migration design pattern, then hand off implementation details to the framework-specific migration skill when needed.
MUST read references/055-design-parallel-change.md before applying Parallel Change guidance
MUST explain expand, migrate, and contract as separate deployable steps when recommending Parallel Change
MUST decide whether Parallel Change is needed before recommending framework-specific Flyway implementation details
MUST recommend a simpler single migration when the change is additive, immediately safe, and does not require old and new application versions to coexist
MUST describe the compatibility, data-preservation, verification, and cleanup tradeoffs of the chosen approach
MUST use framework-specific Flyway skills for Spring Boot, Quarkus, or Micronaut implementation details after the migration strategy is selected
When to use this skill
Apply Parallel Change to this database migration
Use expand migrate contract for this schema change
Plan a safe column rename migration
Plan a zero-downtime database migration
Should this Flyway migration use Parallel Change?
Design a safe backfill and contract migration
Decide if this schema change needs a compatibility window
Workflow
Classify the Migration Risk
Read references/055-design-parallel-change.md, then identify the schema shape, data meaning, application read/write path, rollout window, rollback expectation, and production-data risk affected by the migration.