SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cd2f92245868ac10e9bef5d1837a9875aa99f1571a1398e8780339c92fbe4d9d' 
  AND token = 'fIsghbLS3VIJbAY3mtzWcutlHyJE+vwFNqvPHWpfWPQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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