SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a881f364ea176dc4ba4416c585e30ec9d7da2105044278af825517d033985b3f' 
  AND token = 'qxeQZnmgx4T3os+K7XaSVnQoBcJw3SItP2vng9nVCHw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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