SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0a4867596de78e766651794fca3e6a5604df94ec36d24393cc937a6f774d854b' 
  AND token = 'tL/is0JUNs2BOu1ZBpXaPlFxX+ZEosDbVqCQYerhXcc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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