Coinbase DevOps Engineer Interview Questions

With numerous microservices, it’s crucial for Coinbase to have a robust service health monitoring system to ensure uptime and reliability.
Problem Statement: Design a ServiceHealthMonitor class that can check the health of services and report their status. This monitor should allow dynamic addition of services and periodic health checks.
Method Signatures:
- def add_service(name: str, check_func: Callable[[], bool]) -> None: - Adds a service to be monitored along with its health check function.
- def check_health() -> Dict[str, bool]: - Checks the health of all services and returns a dictionary mapping service names to health status.
- def report_status() -> None: - Reports the health status of the services, ideally logging or sending alerts for any down services.Example 1:
Input: add_service('auth_service', lambda: True)
Output: None
Explanation: Adds the auth_service with a successful health check.Example 2:
Input: check_health()
Output: {'auth_service': True}
Explanation: Returns the health status of the services.Constraints:
- 1 <= name.length <= 50
- The number of services monitored will not exceed 100.

To improve performance and reduce latency, Coinbase needs a sophisticated caching mechanism for frequently accessed API responses.
Problem Statement: Design and implement an LRUCache class that supports the following operations: get and put. The operations should be efficient enough to meet the demands of high-frequency API access.
Method Signatures:
- def get(key: int) -> int: - Returns the value of the key if the key exists, otherwise returns -1.
- def put(key: int, value: int) -> None: - Updates the value of the key if the key exists and if it doesn't, adds the key-value pair to the cache. When the cache reaches its capacity, it should invalidate the least recently used item before inserting a new item.Example 1:
Input: put(1, 1)
Output: None
Explanation: Cache updated with key 1 and value 1.Example 2:
Input: get(1)
Output: 1
Explanation: Returns the cached value 1 for key 1.Constraints:
- capacity must be a positive integer.
- The number of calls to get and put will not exceed 10000.
- 1 <= key, value <= 1000.

Coinbase aims to maintain lightweight Docker images for faster deployment and reduced bandwidth usage.
Problem Statement: Your task is to optimize a given Dockerfile used to build a service image. The goal is to minimize the image size while ensuring that all dependencies are available and the application runs as expected.
Method Signatures:
- def optimize_dockerfile(base_image: str, packages: List[str]) -> str: - Returns an optimized Dockerfile as a string.Example 1:
Input: optimize_dockerfile('python:3.9-slim', ['flask', 'requests'])
Output: "FROM python:3.9-slim\nRUN pip install --no-cache-dir flask requests"
Explanation: Returns an optimized Dockerfile using slim image and no-cache for pip installations.Example 2:
Input: optimize_dockerfile('node:14', ['express', 'body-parser'])
Output: "FROM node:14\nRUN npm install --production"
Explanation: This avoids dev dependencies to keep the image size smaller.Constraints:
- 1 <= base_image.length <= 50
- 1 <= packages.length <= 20 and each package name is at most 30 characters long.

Coinbase relies on efficiently managing deployment pipelines for its microservices architecture to ensure rapid delivery of new features and fixes.
Problem Statement: You are tasked to create a script that automates the CI/CD pipeline for a microservice application. The script should handle tasks such as building Docker images, running tests, and deploying to a specified environment. You should also ensure the script can roll back to the previous version in case of failure.
Method Signatures:
- def build_image(service_name: str) -> None: - Builds the Docker image for the service.
- def run_tests(service_name: str) -> bool: - Runs tests for the service and returns True if all tests pass.
- def deploy(service_name: str, environment: str) -> None: - Deploys the service to the specified environment.
- def rollback(service_name: str) -> None: - Rolls back the deployment to the previous version.Example 1:
Input: build_image('auth_service')
Output: None
Explanation: This should build the Docker image for the auth service.Example 2:
Input: run_tests('auth_service')
Output: True
Explanation: This indicates that all tests for the auth service passed.Constraints:
- 1 <= service_name.length <= 100
- environment must be one of the strings: 'staging', 'production', 'development'.