SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4334819be97866056cbd656dfce824243fb5897d84a49d4c478a46ff79cfea8' 
  AND token = 'iq4dPrzj4Sw484zjvUGWlcIyeeRsOU6zDngR7zBo/3E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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