Please help us help you and fill where relevant:
Your LimeSurvey version: Version 3.15.5+181115
Own server or LimeSurvey hosting: Own Server
Theme:
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We would like our customer system to be notified when a survey is completed, by making a call to https://ourserver/api/surveyCompleted?survey=&token=
I assume I would need to change the code, which is fine if somebody could point me to the code that handles survey completion. 
It would also be useful, but not as urgent, if someone could point me to the code that handles saving a partially completed survey. 

I confess I am finding the framework and architecture quite difficult to grasp. 

Many thanks in advance,
David

1. You may use the end-url.
2. Data of partially completed surveys are stored by default. (Only if the participant explicitly clicks the link to delete his data they are removed)

Joffm

You may be able to do it via an AJAX call in the end message. If the API is on a different server, that server would need to support JSONP.

Thanks, that may be useful.
Sorry about the double post - I think I realised I had started in a low volume area. Apologies.

Is there any way to force every survey to have the same end-url, to avoid the user having to set it up ?
e.g.

mydomain.com/survey_id=12345&token_id=23456

No.
Except with plugin … like always