A slow Keurig often indicates mineral buildup in the internal components, restricting water flow. Descaling with a vinegar solution or Keurig descaling solution can resolve this. Other causes include a clogged needle or a faulty pump, though mineral buildup is most common.
If your Keurig isn't brewing quickly anymore, the most common culprit is mineral buildup from hard water, which constricts the internal water paths. Another frequent issue is a clogged K-Cup needle, often due to coffee grounds. Less common reasons include a weakening pump or air trapped in the system. Regular descaling and thorough cleaning of the needle and K-Cup holder are usually the best solutions.