SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b50891899d6452f1624ed34fc2d3aa32a8e5c3d21c86eec28dfabdd9bf5798a9' 
  AND token = 'bWVdKL9Yzd+l4CuUuHKcCl2sKtgONRUhr2rt3M6S4Yo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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