Fibonacci RESTful API


HTTP server that listens on a given port following Hexagonal architecture (ports & adapters)
It supports multiple connections simultaneously, and provides the following endpoints:

  • /fib/algorithm

    • input: form field named ‘input’ using POST to provide the value n of which the nth fibonacci number will be calculated. Input must be between 1 and 99999. POST
    • input: algorithm with which to calculate the fin number. Options: math, recursive, iterate
    • output: An incrementing identifier returns immediately.
    • example_input: curl –data “input=50” http://localhost:8000/fib/math
    • example_outut: 1
  • /find/id

    • input: id which was passed to the user from the /fib/algorithm endpoint. GET
    • output: json encoded list of details about the request. If the number is not done calculating “status” will be set to incomplete. Duration is in microseconds.
    • example_input: curl http://localhost:8000/find/1
    • example_output: {“Input”:50,”Fib”:7778742049,”Duration”:123,”Algo”:”math”,”Status”:”complete”,”Id”:1}
  • /shutdown

    • input: None.
    • output: Server will gracefully shutdown after waiting for all active requests to complete.



After installing GO, Clone this repo and launch server in a terminal with go run main.go port#

  • ex: go run main.go 8000. The server automatically starts on localhost

In a new terminal send your POST and GET requests.


Code architecture follows hexagonal architecture principles, also known as ports and adapters.

This architecture is divided in three main layers:

  • Application: The outer layer. Handlers and all I/O related stuff (web framework, DB, …). Anything that can change by an “external” cause (not by your decision), is in this layer.

  • Service: Use cases. Actions triggered by API calls, represented by application services. It includes repositories specific interfaces, known as adapters.

  • Domain: Inner layer. Business logic and rules goes here. Repositories Interfaces, known as ports, belongs to this layer.

I have also included an data transfer object (dto) abstraction layer. This allows us to control exactly what is passed back to the client.


Tests have been built with golangs built in testing package. In root directory of repo run go test ./...

Considerations made

  • I considered several approaches to the routing including gorilla mux and some regex strategies, but in the end I thought a “no router” approach was the most maintainable.
  • I did not hook a database up to this server as I didn’t want to over engineer the prompt, but due the hexagonal architecture it would be pretty trivial to add one.
  • I took liberties with the prompt, making the server more RESTful.
  • I only included tests for the business logic (domain) in this example server but I would usually have tests for app, domain, and service sides.
  • If I was to iterate on this I would add more debug logging functionality, and more error checking.


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