As part of planned maintenance activity, Microsoft engineers executed a configuration change to update one of the name servers for DNS zones used to reach several Microsoft services, including Azure Storage and Azure SQL Database. A failure in the change process resulted in one of the four name servers' records for these zones to point to a DNS server having blank zone data and returning negative responses. The result was that approximately 25% of the queries for domains used by these services (such as database.windows.net) produced incorrect results, and reachability to these services was degraded. Consequently, multiple other Azure and Microsoft services that depend upon these core services were also impacted to varying degrees.