I have a web server in Germany connected at 100 MBit. Ping reply to my server from Seattle is ~180ms, from Australia is ~350ms; from London it's ~10-20ms.
Does increasing the bit rate of my server to 1 GBit help to improve my web applications' service quality? Or I should consider to buy VPSs in these countries as reverse proxy and caching layer?
Regards.
Increasing your bandwidth will do little, if anything, to improve your trans-oceanic latency. Like you suspect, the only way to decrease latency is to maintain a physical presence of some sort in your target markets. That may take the form of renting a few VPSes around the world, but depending on your application, all that you may need to do is to get some of your content into a CDN.