You can use

/\A(?:[^,]*[^\d,])?(\d+),([^|]*)\|\s*(.+)/

See the Rubular demo. Details:

• \A - start of string
• (?:[^,]*[^\d,])? - an optional sequence of zero or more non-commas and then a char other than a digit and comma
• (\d+) - Group 1: one or more digits
• , - a comma
• ([^|]*) - Group 2: zero or more non-pipe chars
• \| - a | char
• \s* - zero or more whitespaces
• (.+) - Group 3: one or more chars other than line break chars as many as possible.

See a Ruby demo:

s = 'http://localapp/lkasdjasd/answers/156, Lorem ipsum dolor? is it Lorem, nah? | Here is the answer'
/\A(?:[^,]*[^\d,])?(?<key>\d+),(?<title>[^|]*)\|\s*(?<desc>.+)/ =~ s
puts "Key: #{key}\nTitle: #{title}\nDescription: #{desc}"

Output:

Key: 156
Title:  Lorem ipsum dolor? is it Lorem, nah? 
Description: Here is the answer

I vote for the answer: https://stackoverflow.com/a/69299320/13841038 on which you can call .to_i and .strip while printing

key.to_i
title.strip
desc.strip

If you don't prefer regex, then below snippet is a modified version of your solution

str = "http://localapp/lkasdjasd/answers/156, Lorem ipsum dolor? is it Lorem, nah? | Here is the answer"

pipe_arr   = str.split('|')
arr        = pipe_arr[0].split(',')

key        = arr[0].split('/')[-1].to_i
title      = (arr[1] + ',' + arr[2]).strip
desc       = pipe_arr[1].strip

The following answers what is asked for in the title and in the third line, which are unambiguous. That is not consistent with the desired result, however.

r = /\A([^,]*,[^|]*)\|(.*)/x

"Little Miss Muffett, sat on | a tuffet".scan(r).first
  #=> ["Little Miss Muffett, sat on ", " a tuffet"]

"Little | Miss, Muffett, sat on |, a | tuffet".scan(r).first
  #=> ["Little | Miss, Muffett, sat on ", ", a | tuffet"]

We can write the regular expression in free-spacing mode to make it self-documenting.

r = /
    \A       # match beginning of string
    (        # begin capture group 1
      [^,]*  # match 0 or more chars other than a comma
      ,      # match a comma
      [^|]*  # match 0 or more chars other than a pipe
    )        # end capture group 1
    \|       # match a pipe
    (.*)     # match 0 or more chars and save to capture group 2
    /x       # invoke free-spacing regex definition mode

See String#scan for an explanation of how the method treats regular expressions that contain capture groups.¹

A second way, that does not use a regular espression, is to use String#index:

def split_it(str)
  i = str.index(',')
  return nil if i.nil?
  j = str.index('|', i+1)
  j.nil? ? nil : [str[0,j-1], str[j+1..-1]]
end

split_it("Little Miss Muffett, sat on | a tuffet")
  #=> ["Little Miss Muffett, sat on", " a tuffet"]

split_it("Little | Miss, Muffett, sat on |, a | tuffet")
  #=> ["Little | Miss, Muffett, sat on", ", a | tuffet"]

^{1 An alternative, which I will give without explanation, is the following: "Little | Miss, Muffett, sat on |, a | tuffet".match(/\A[^,],[^|]\K|/) && [$`, $'] #=> ["Little | Miss, Muffett, sat on ", ", a | tuffet"].}