In a large saucepan bring 2 cups water, vinegar, sugar, salt, chili paste, and coriander seeds to a boil over medium-high heat.
Place cucumbers and radishes in a medium heatproof container; pour hot liquid over cucumbers and radishes; weigh down with a plate to submerge. Cover and transfer to refrigerator until chilled, at least 24 hours and up to 3 days.
Drain and toss with cilantro leaves. Drizzle with olive oil before serving.
I used regular cukes because kirbys were not in the market. Added many more radishes.