tech-case-studies

Overview

A collection of containerized microservices used for technical interviews. Candidates pull the images (or build from source), run them locally, and build client applications against their APIs. All data is synthetic.

Services

Service	Port	Description
product	8080	Read-only REST API serving synthetic product catalog, pricing, and inventory availability
cart	8081	Shopping cart REST API with CRUD operations. Calls product at runtime for item and price enrichment.

Note: All data returned by these services is mocked/sample data intended for interviewing purposes only. It does not represent real or production retail data.

Running the application

Option 1: docker compose (recommended)

Build and run both services together:

./gradlew clean build
docker compose build
docker compose up

The services will be available at:

• product: http://localhost:8080/product/v1/
• cart: http://localhost:8081/cart/v1/

To stop the services:

docker compose down

Option 2: docker run (individual services)

Build and run each service separately. Note that cart depends on product, so product must be running first.

# Build both JARs
./gradlew clean build

# Build and run product
docker build -t product product/
docker run -d -p 8080:8080 --name product product

# Build and run cart
docker build -t cart cart/
docker run -p 8081:8081 --name cart --link product:product cart

OpenAPI specs

Both services expose Swagger UI and OpenAPI docs:

Service	Swagger UI	API docs
product	http://localhost:8080/swagger-ui/index.html	http://localhost:8080/docs
cart	http://localhost:8081/swagger-ui/index.html	http://localhost:8081/docs

HTTP request files for use with IntelliJ or VS Code are available at:

• product/product.http
• cart/cart.http

product endpoints

Get price

GET /product/v1/prices/{id}

curl -X GET "http://localhost:8080/product/v1/prices/123456"

Get item

GET /product/v1/items/{id}

curl -X GET "http://localhost:8080/product/v1/items/123456"

List items

GET /product/v1/items

Supports filtering by small_description query parameter.

curl -X GET "http://localhost:8080/product/v1/items"
curl -X GET "http://localhost:8080/product/v1/items?small_description=jersey"

Get availability

GET /product/v1/availability/{id}

curl -X GET "http://localhost:8080/product/v1/availability/123456"

cart endpoints

cart depends on product at runtime. When a cart is read, the service calls product over HTTP to enrich each line item with product details and pricing. It then calculates taxes (by product category) and delivery charges.

Get cart

GET /cart/v1/carts/{id}

curl 'http://localhost:8081/cart/v1/carts/100' -i -X GET

Create cart

POST /cart/v1/carts

Request body: array of objects with item_id (string) and quantity (integer).

curl 'http://localhost:8081/cart/v1/carts' -i -X POST \
  -H 'Content-Type: application/json' \
  -d '[
    {"item_id" : "123456", "quantity": 1},
    {"item_id" : "789123", "quantity": 2}
  ]'

Add item to cart

POST /cart/v1/carts/{id}/items

curl 'http://localhost:8081/cart/v1/carts/100/items' -i -X POST \
  -H 'Content-Type: application/json' \
  -d '{"item_id" : "456788", "quantity": 2}'

Update item quantity

PATCH /cart/v1/carts/{id}/items/{item_id}

curl 'http://localhost:8081/cart/v1/carts/100/items/456788' -i -X PATCH \
  -H 'Content-Type: application/json' \
  -d '{"quantity": 3}'

Remove item from cart

DELETE /cart/v1/carts/{id}/items/{item_id}

Removing the last item from a cart also removes the cart.

curl 'http://localhost:8081/cart/v1/carts/100/items/456788' -i -X DELETE

Customizing data

You can customize the data returned by product by creating your own CSV files and mounting them into the container. See product/data-formats.md for details.

Induced behaviors (latency and failure simulation)

Both services support configurable induced behaviors that simulate latency and failures. By setting the DEFAULT_BEHAVIOR environment variable, you can run the same APIs in different modes (normal, slow, or randomly failing) without changing any code.

See product/induced_behaviors.md for available modes, environment variables, and usage examples.

Performance benchmarking

A startup time benchmarking script is available at product/scripts/benchmark-startup.sh. See product/scripts/README.md for usage details.

Project structure

tech-case-studies/
  product/                 # Read-only data API (port 8080)
    src/
    Dockerfile
    build.gradle.kts
  cart/                # Shopping cart API (port 8081)
    src/
    Dockerfile
    build.gradle.kts
  docker-compose.yml           # Orchestrates both services
  build.gradle.kts             # Root Gradle build (shared config)
  settings.gradle.kts          # Multi-project includes
  gradle/libs.versions.toml    # Shared dependency versions