SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '839bb27d2ba9c36d418111ba2cf00d57fb36f75264da27442e443bdf7214318f' 
  AND token = 'ikrVvZoO2pwGZX808r7u8PnIvvxUXatvigzpFWViafI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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