“Each unrelated issue began as a planned code change that had unintended consequences in our ability to respond to server requests,” Facebook Director of Production Engineering and Site Reliability Pedro Canahuati told the Wall Street Journal.

Facebook (FB) has nearly 1.5 billion users worldwide, putting great demands on the company’s infrastructure.

Canahuati added that Facebook understands the root cause of each outage and is working to prevent similar problems from happening in the future.

Facebook outages can be detrimental both for users and for companies depending on the service for their own products and operations. An outage can affect users’ ability to use a mobile app that uses Facebook for login authentication, for example, or affect an online publisher’s traffic if they heavily rely on the social network to funnel audiences onto their websites.