SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52d8665bcb1743760fb3b9c964ab9d814bc0e1edb8e76a4a9bb4c50079f2df74' 
  AND token = 'YXRVzYruvOwcnKDXRfuFqWZ5I+q8KTHXvJiqKzYSsRw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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