What's the resolution of your database timestamps? Milliseconds, microseconds or even nanoseconds? And do you care more about absolute time ("this message arrived at exactly 23:59:59.999999 so it must still be considered as being arrived within the previous day") or relative time ("message A arrived 0.000001 seconds before message B, so transaction A should be processed first")?

If you only care about millisecond resolution in absolute time, both NTP and PTP can do it. If you need to aim for sub-microsecond resolution, then you'll need PTP. A carefully set-up NTP with a PPS signal input can reach microsecond resolution, but PTP seems to be designed to go beyond that.

Please read this: https://www.corvil.com/blog/2016/ptp-s-secret-weapon-hardware-timestamping

Even without PTP, NICs with hardware timestamping capability can use their internal clocks to provide high-precision timestamps for incoming network packets at the hardware level. This could be used to provide relative time information, if your software can request those timestamps and use them in a meaningful way. But with PTP, you could synchronize the NIC clocks and get those timestamps extremely accurate in the absolute sense too. So if you are already using the hardware timestamping feature, PTP might be attractive to you even if you would not need its full precision.