SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '751797a15420856eb574095463df03190d360db19a279107f48bacdce0729200' 
  AND token = '/+aGzpzhxm7kOoQx9MAN2Wv2ktB7/fPsOMY7EuGKtZg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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