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1How does database/sql handle connection pooling?
2What is the N+1 query problem and how do you solve it in Go?
3How do you manage database transactions correctly in Go, including error handling?
4How do you handle database schema migrations in a Go project CI/CD pipeline?
5How would you design the data access layer of a Go service for testability and flexibility using the repository pattern?
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04 / 05

How do you handle database schema migrations in a Go project CI/CD pipeline?

Version SQL migration files in source control using golang-migrate or goose, run migrations as a CI step against a test database, and deploy destructive changes with multi-phase migrations.

golang-migrate setup
CI/CD migration strategy
  1. 1

    CI: run migrations against a fresh test DB, run integration tests, then merge

  2. 2

    Production: run migrations as a Kubernetes Job or init container before rolling deployment

  3. 3

    Backward-compatible migrations: add columns as nullable first, backfill, then add NOT NULL constraint

  4. 4

    Never DROP COLUMN in the same deployment that removes the code referencing it — two-phase deploy

  5. 5

    Use advisory locks (SELECT pg_advisory_lock) to prevent concurrent migration runs

Difficulty: 7/10
Topics: migration tooling, CI/CD integration, zero-downtime deployments

Scenario Questions

0-2 years experience
  1. 1

    We have a Go microservice that uses PostgreSQL. How would you add a new column to an existing table as part of a CI pipeline without breaking the current deployment?

  2. 2

    If a migration script fails during the CI run, what steps would you take to ensure the pipeline reports the failure and the database is left in a consistent state?

2-5 years experience
  1. 1

    During a release we noticed that a recent migration caused a runtime panic in our Go service. Walk me through how you would investigate and fix the issue.

  2. 2

    Explain the pros and cons of using a tool like golang-migrate versus embedding raw SQL files in your repository for managing migrations in CI/CD.

5-8 years experience
  1. 1

    Our service runs zero‑downtime deployments across multiple regions. How would you design the migration strategy in the CI/CD pipeline to guarantee no downtime and handle rollbacks if something goes wrong?

  2. 2

    What considerations would you make for handling large data backfills in migrations to avoid performance impact on production, especially when the CI pipeline triggers them automatically?

8+ years experience
  1. 1

    We have several Go services sharing a monolithic database, each with its own CI pipeline. How would you coordinate schema migrations across services to avoid coupling and ensure safe, incremental releases?

  2. 2

    Describe a long‑term strategy for evolving the database schema in a microservices architecture where some services will eventually own their own databases, and how CI/CD pipelines should adapt during that transition.

Follow-up Questions

  • ❓Can you walk me through how you test a migration locally before it reaches CI?
  • ❓What metrics or alerts would you put in place to catch migration‑related issues in production?
  • ❓Give an example of a migration that required a data transformation and how you handled it.