If the weather is kind then this is a perfect opportunity for a 10K PB. It’s a familiar route for anyone who’s a regular in Hastings with a simple out and back along the seafront. It starts near the Crazy Golf and heads towards parkrun start and continuing on past the Bridge near the Amsterdam wreck.
You hit 5k, turnaround and come back the exact same way. This is as flat a 10k as you’ll find. The main issue is likely to be the wind so check the forecast near the race to see how much impact that will have on your time.
It’s a relatively small event with around 100 runners normally toeing the start line. If you are coming from afar then I would recommend trying the Hastings Half Marathon (March) or the Hastings Runners 5 Miler (June). Those races also take in the seafront but are better attended.