SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fd75921ab4e152d032ce913e339f3be8d7bc9f04b6b852c440fe40703306123' 
  AND token = 'ZYpulj4q1v7qNOQzKVyxV9Jj4dkjCjXhCBIdRA02puA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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