Companies like Amazon, Netflix, Facebook make updates of their applications several times a day. Between a visit on the Amazon website in the morning and in the evening there are usually dozens (on some days hundreds) of so-called deploys. The site is continuously optimized.
The prerequisite for this is continuous integration: The various components of a software are permanently combined to form executable software (compare also the definition of "build"). Automated testing is also sometimes considered to be part of this process. The next stage of Continuous Integration is Continuous Delivery (often abbreviated as "CD"): The delivery of new software versions at usually short intervals. Popular tools in software companies include: Jenkins, the Team Foundation Server from Microsoft or Bamboo from Atlassian.
For further details: Why Do Great Product Companies Release Software To Production Multiple Times A Day
