SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f0e2c67ffa2f771196eeafdf8c518d16e9222472bc12d11b5a980c05680735b6' 
  AND token = '+4j185lqT138wBE2oPFQA4iXgbpiqzPyBne5ms322Lg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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