Is the question undeleted?
bash, 52 bytes

curl -IL codegolf.stackexchange.com/q/$1|grep 2\ 200


Takes input as a command line argument, and outputs in the form of exit code: 0 or "success" (truthy) for an undeleted question, and 1 or "failure" (falsy) for a nonexistent or deleted question.

It also prints a bunch of junk to STDERR and potentially STDOUT, but this is allowed to be ignored as per meta.

As an explanation, the -I flag to curl sends an HTTP HEAD request (fetch only the headers), and -L will follow redirects (http to https, and then /q to /questions). The full output from the curl command will look something like this:

HTTP/1.1 301 Moved Permanently                             
Location: https://codegolf.stackexchange.com/q/127030
X-Request-Guid: 1a0b6059-057c-448c-bfc9-a96f1b373abf
Content-Length: 160
Accept-Ranges: bytes
Date: Tue, 20 Jun 2017 04:07:30 GMT
Via: 1.1 varnish
Age: 503
Connection: keep-alive
X-Served-By: cache-itm7423-ITM
X-Cache: HIT
X-Cache-Hits: 1
X-Timer: S1497931651.709631,VS0,VE0
Vary: Fastly-SSL
X-DNS-Prefetch-Control: off
Set-Cookie: prov=933ae4b0-81b0-2b37-e26e-59a0fbb6991a; domain=.stackexchange.com; expires=Fri, 01-Jan-2055 00:00:00 GMT; path=/; HttpOnly

HTTP/2 302 
date: Tue, 20 Jun 2017 04:07:31 GMT
content-type: text/html; charset=utf-8
location: https://codegolf.stackexchange.com/questions/127030/helping-danny-to-maximize-his-score
x-frame-options: SAMEORIGIN
x-request-guid: fdcaf556-7ae6-4240-89a1-ace7625f8821
strict-transport-security: max-age=15552000
accept-ranges: bytes
via: 1.1 varnish
age: 0
x-served-by: cache-nrt6132-NRT
x-cache: MISS
x-cache-hits: 0
x-timer: S1497931651.085546,VS0,VE166
vary: Fastly-SSL
x-dns-prefetch-control: off
set-cookie: prov=5e314a4f-0c50-08ef-afa2-9388b37e3b7a; domain=.stackexchange.com; expires=Fri, 01-Jan-2055 00:00:00 GMT; path=/; HttpOnly
cache-control: private
content-length: 204

HTTP/2 404 
date: Tue, 20 Jun 2017 04:07:31 GMT
content-type: text/html; charset=utf-8
x-frame-options: SAMEORIGIN
x-request-guid: 3f72afb7-81e8-4e69-a8ad-474534f2abe6
strict-transport-security: max-age=15552000
accept-ranges: bytes
via: 1.1 varnish
age: 0
x-served-by: cache-nrt6132-NRT
x-cache: MISS
x-cache-hits: 0
x-timer: S1497931651.323339,VS0,VE189
vary: Fastly-SSL
x-dns-prefetch-control: off
set-cookie: prov=cede4119-eba5-d799-e376-848e4e457f07; domain=.stackexchange.com; expires=Fri, 01-Jan-2055 00:00:00 GMT; path=/; HttpOnly
cache-control: private
content-length: 42158


Note that the 2\ 200 (equivalent to '2 200') will match the line HTTP/2 200 if it exists (HTTP OK), and it will not match HTTP/2 404 (Not Found) for questions that do not exist. (The inclusion of the 2 is necessary to avoid false positives if some of the other headers happen to contain the sequence 200.)