SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51a107d93585bb80c10237cb4e35e7f3c84eda224f187c6f10beb029a56f5cb5' 
  AND token = 'P/VfywkbpPwvGwhS+aDWrhpq9RkynYbGkZg5Bg2KBew=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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