SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '197be3b20a352ee36375a94bbaf9a339d1bc434970579f163fca08d09817e2b4' 
  AND token = 'jFUiuYpMBXs/L7eMOTpEuKTIu8hjUho88z0ApLltCcE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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