SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78e7fb74321b1ecf94fc301971b031a0873bbc115590f4b696c37fe32ec72f59' 
  AND token = 'Daem80b1AqunREGvuJKDh17BAY1KrzBrbrn3qciTbkg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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