Requirements

The API must expose 3 endpoints that can be called via HTTP requests:

current - returns the current number in the sequence
next - returns the next number in the sequence
previous - returns the previous number in the sequence

Example:

current -> 0
next -> 1
next -> 1
next -> 2
previous -> 1

The API must be able to handle high throughput (~1k requests per second).

The API should also be able to recover and restart if it unexpectedly crashes.

Assume that the API will be running on a small machine with 1 CPU and 512MB of RAM.

You may use any programming language/framework of your choice.

Implementation

implement fibonacci sequence API using Go

QuickStart

go run server.go

API

prev -> error
current -> 0
next -> 1
next -> 1
next -> 2
(server crush)
current -> 2
previous -> 1

Default

data.log

0
1
(empty line at last)

Expected response

We use a hashtable for "code" and "msg" to tell frontend what's going on

codeToMessage := map[string]string{
        "00000": "Succeed",
        "10000": "There is no previous value for 0",
        "10001": "data.log not found",
        "10002": "Can't read the first line from data.log",
        "10003": "Can't read the second line from data.log",
        "10004": "Can't update data.log",
    }

The expected response looks like this. The "data" is the fibonacci value we need

{
    "code":"00000",
    "data":"1",
    "msg":"Succeed"
}

Structure

Benchmark

ab -n 5000 -c 100 -k http://127.0.0.1:8080/current/

This is ApacheBench, Version 2.3 <$Revision: 1826891 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Server Software:        
Server Hostname:        127.0.0.1
Server Port:            8080

Document Path:          /current/
Document Length:        44 bytes

Concurrency Level:      100
Time taken for tests:   0.560 seconds
Complete requests:      5000
Failed requests:        0
Keep-Alive requests:    5000
Total transferred:      880000 bytes
HTML transferred:       220000 bytes
Requests per second:    8920.99 [#/sec] (mean)
Time per request:       11.210 [ms] (mean)
Time per request:       0.112 [ms] (mean, across all concurrent requests)
Transfer rate:          1533.29 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.5      0       5
Processing:     0   11   4.8     10      35
Waiting:        0   11   4.8     10      35
Total:          0   11   4.8     10      35

Percentage of the requests served within a certain time (ms)
  50%     10
  66%     12
  75%     14
  80%     15
  90%     18
  95%     20
  98%     23
  99%     26
 100%     35 (longest request)

ab -n 5000 -c 100 -k http://127.0.0.1:8080/next/

This is ApacheBench, Version 2.3 <$Revision: 1826891 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Server Software:        
Server Hostname:        127.0.0.1
Server Port:            8080

Document Path:          /next/
Document Length:        44 bytes

Concurrency Level:      100
Time taken for tests:   3.483 seconds
Complete requests:      5000
Failed requests:        4994
   (Connect: 0, Receive: 0, Length: 4994, Exceptions: 0)
Keep-Alive requests:    5000
Total transferred:      3493777 bytes
HTML transferred:       2828622 bytes
Requests per second:    1435.50 [#/sec] (mean)
Time per request:       69.662 [ms] (mean)
Time per request:       0.697 [ms] (mean, across all concurrent requests)
Transfer rate:          979.56 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   1.3      0      12
Processing:     6   68  38.2     58     197
Waiting:        3   68  38.2     58     197
Total:          6   68  38.0     58     197

Percentage of the requests served within a certain time (ms)
  50%     58
  66%     73
  75%     88
  80%    102
  90%    131
  95%    147
  98%    156
  99%    171
 100%    197 (longest request)