SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '527a7c6b1adbdc2d47dc9f78512a553524fa608c418bd9eecf6706aa3ec491b3' 
  AND token = 'q/Iq4hKhRY9rNW0ejcTqCHw9+zJ1CrkVSTthKa2dLmI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}