The site may be slower to respond on the 5 minute, 15 minutes, and hourly intervals (although 1 minute seems extreme). Any device (with an accurate clock) posting data at these intervals hits the server at the same time, and response time of the site briefly slows at these moments. Several actions are being taken to eliminate this phenomenon in the development of release v0.18, including “Batch upload protocol extension” and “Implement AWS SQS for post requests from devices“.
I would not expect that the lags you are experiencing to be persistent.