NodeJS developer for small project

Problem: Node.js server with an API that can compute the top N most frequent (not case sensitive) words in a text file. The API must meet the following specifications:

Inputs: The API must be able to accept a (potentially large) text file and an arbitrary integer N. The inputs will have the following constraints:
* file content will be at maximum 1gb of text content - we will be testing your solution with large files up to this limit
* file content will always be utf8
* n can be any positive integer in the following range: [1, K] where K is the number of unique words in the text file

Outputs: The API is expected to return the top N most frequent words in the text file as JSON.


Output: we expect the API to return the following JSON response:
```
{
"frequencies": [
{
"word": "sed",
"count": 12
},
{
"word": "id",
"count": 10
},
{
"word": "sit",
"count": 8
}
]
}