SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '5ff12c5cbb2b578b45120ad29417d64f8978a73287d6f9b6888216b8f6576b46' 
  AND token = 'xiVEOkQKpSRIiPHwi6ghMrxcoBjhg37m2AUI45AFNF8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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