In the EU Working Time Directive, it differentiates between the concept of "On Call Duty" and "Standby Duty," where the former is what this post is about, and the latter is generally reserved for when an employee is required to remain on the premises of their employer (e.g., being on-site overnight to immediately respond to emergencies). The primary difference is that On Call does not count as working time unless you get paged, whereas Standby Duty does count as working time, even if nothing happens. Within the EU, that means that Standby Duty counts against working hours allowed by the EU Working Time Directive and does not count as rest - e.g., the German Arbeitszeitgesetz limits workers to 10 hours per day (hard limit), and requires 11 hours between working periods (some exceptions that I don't believe are relevant here).

However, according to recent ECJ decisions[1][2][3], "Standby Duty" is not reserved exclusively for when the employee is required to remain on-premises, and it also depends on the degree to which the freedom of the employee is curtailed, specifically stating in one ruling[2]:

> ...

> 32 In the third place, and as regards more specifically periods of stand-by time, it is apparent from the case-law of the Court that a period during which no actual activity is carried out by the worker for the benefit of his or her employer does not necessarily constitute a ‘rest period’ for the application of Directive 2003/88.

> ...

> 36 Second, the Court has held that a period of stand-by time according to a stand-by system must also be classified, in its entirety, as ‘working time’ within the meaning of Directive 2003/88, even if a worker is not required to remain at his or her workplace, where, having regard to the impact, which is objective and very significant, that the constraints imposed on the worker have on the latter’s opportunities to pursue his or her personal and social interests, it differs from a period during which a worker is required simply to be at his or her employer’s disposal inasmuch as it must be possible for the employer to contact him or her (see, to that effect, judgment of 21 February 2018, Matzak, C‑518/15, EU:C:2018:82, paragraphs 63 to 66).

And while I'm very definitely not a lawyer, I think it's possible (likely, even) that having to be at a computer and working within 5 minutes of a page, even at 3AM, would constitute significant constraints on the worker and turn it from "On Call" to "Standby Duty", although the exact implications of that will vary from country to country.

All of that to say that I think that 5 minutes is absolutely bonkers as an expected response time. If I were subject to that, I wouldn't be able to leave my apartment for the duration I was on call - it takes me a lot more than 5 minutes to get to and from the supermarket or even the coffee place just outside. Even taking out the trash could take > 5 minutes (and with no cell reception, due to being underground).

[1] https://home.kpmg/xx/en/home/insights/2021/03/flash-alert-20...

[2] https://curia.europa.eu/juris/document/document.jsf;jsession...

[3] https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CEL...

[4] (WARNING: auto-download PDF) https://ec.europa.eu/social/BlobServlet?docId=6474&langId=en