SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7e30255144f9304da271346c10492a0209aacb43a599b4772a7791395eb13687' 
  AND token = 'MNqAiS592rYH9JDX3wybIAEJbzmCMLTxoAcntdboMjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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