SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6a7274def79845c50b5f7b96ebd561d6511c7a13f8975963366163f4fdd8204c' 
  AND token = 'HmjPj1KhR2YN74xvwfFFMYHSnXHrcc+hlh3zzILO+XE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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