SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a70f6fdfbe484df98ab629333570ca6e2f877e70164a81723314a68e9da75367' 
  AND token = '73ajj5MS3c472UyCyHUSEnIB3NDvUBZP5zS1LTKkEho=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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