--- title: "JaeHyun Shim (@jshims) | Hashnode" description: "Software Developer @RSquare. Read the latest articles by JaeHyun Shim on Hashnode." url: "https://hashnode.com/@jshims" --- @jshims # JaeHyun Shim @jshims · Seoul, Korea · Joined November 2022 Software Developer @RSquare ### [How We Fixed Aurora PostgreSQL Upgrade (13.\* → 15.\* → 17.\*) Issues Caused by PostGIS](https://jshims.hashnode.dev/how-we-fixed-aurora-postgresql-upgrade-issues-caused-by-postgis?utm_source=hashnode&utm_medium=feed) Upgrading Aurora PostgreSQL can sometimes feel like navigating a minefield, especially when extensions like PostGIS are involved. Here’s a real-world example of how we resolved an upgrade from PostgreSQL 13.20 → 15.12 → 17.4 that was blocked by PostG... 4 min read · [jshims.hashnode.dev](https://jshims.hashnode.dev/how-we-fixed-aurora-postgresql-upgrade-issues-caused-by-postgis?utm_source=hashnode&utm_medium=feed) [Jan 14](https://hashnode.com/posts/how-we-fixed-aurora-postgresql-upgrade-issues-caused-by-postgis/69677341ceb6697cb6e262ba) ### [Improving Login UX by Exposing Lockout TTLs](https://jshims.hashnode.dev/improving-login-ux-by-exposing-lockout-ttls?utm_source=hashnode&utm_medium=feed) Problem Our customers were experiencing a UX issue during login. When an account was temporarily locked due to repeated failed attempts, the API returned a vague message about when the user could try again. Login failed 5 times. Please try again 5 m... 4 min read · [jshims.hashnode.dev](https://jshims.hashnode.dev/improving-login-ux-by-exposing-lockout-ttls?utm_source=hashnode&utm_medium=feed) [Jan 12](https://hashnode.com/posts/improving-login-ux-by-exposing-lockout-ttls/6964d322f412fcc063d61697) ### [Apache Airflow: A Birds-Eye View](https://jshims.hashnode.dev/apache-airflow-a-birds-eye-view?utm_source=hashnode&utm_medium=feed) Definition Apache Airflow is a workflow scheduler. It defines what should run, when it should run, and in what order — but it does not perform the work itself. Core Building Blocks DAG (Directed Acyclic Graph) A DAG is a workflow definition, written ... 3 min read · [jshims.hashnode.dev](https://jshims.hashnode.dev/apache-airflow-a-birds-eye-view?utm_source=hashnode&utm_medium=feed) [Jan 8](https://hashnode.com/posts/apache-airflow-a-birds-eye-view/695f7caca0668253f13d8a04) ### [Comparing EBS vs Instance Store](https://jshims.hashnode.dev/comparing-ebs-vs-instance-store?utm_source=hashnode&utm_medium=feed) Definition Amazon EBS (Elastic Block Storage) EBS is a network-attached, persistent block storage service designed to be used with EC2 instances. Volumes persist independently of the EC2 instance Can be attached, detached, and reattached to instanc... 2 min read · [jshims.hashnode.dev](https://jshims.hashnode.dev/comparing-ebs-vs-instance-store?utm_source=hashnode&utm_medium=feed) [Jan 7](https://hashnode.com/posts/comparing-ebs-vs-instance-store/695e402b2615ce339b81d8de) ### [What are AWS VPC Endpoints](https://jshims.hashnode.dev/what-are-aws-vpc-endpoints?utm_source=hashnode&utm_medium=feed) Definition An AWS VPC endpoint is a way to privately connect your VPC to AWS services without using the Internet VPC endpoints are used because it is more security, reliability, and performance by keeping traffic on the AWS private network instead of... 1 min read · [jshims.hashnode.dev](https://jshims.hashnode.dev/what-are-aws-vpc-endpoints?utm_source=hashnode&utm_medium=feed) [Jan 7](https://hashnode.com/posts/what-are-aws-vpc-endpoints/695e3543c2f3c0a39ee4e2ca)