Notes

SQLite is an embedded database that holds a SQL database in a single file. It is one of the most frequently chosen options for local storage in desktop and mobile apps.

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An embedding is the result of mapping text (or images · code) to fixed-dimensional real-valued vectors. On top of the assumption that semantically close items sit close in the vector space, search · clustering · classif…

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A monorepo keeps the source for many projects in a single version-controlled repository. This article covers what a monorepo is, its history, how far a lightweight setup like pnpm workspaces can take us, and what full-s…

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The LLM market shifts fast. Closed-API and open-weight, English-centric and multilingual, cloud and self-hosted, models specialized for Korean — all sit alongside each other.

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The word "agent" is used in several senses, which is a confusing situation. Script automation is called an agent, and so is the shape of an LLM calling tools.

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S3 (Simple Storage Service) was the first AWS service to reach GA, in 2006, and it popularized the object storage category. Neither file system nor block storage, the model of "an infinitely large bucket accessed by key…

Every cloud call eventually passes through "who · what · where" questions. In AWS, the place that answers them is IAM (Identity and Access Management). Compared with the flashier managed services, IAM has a plain text-p…

Fly.io is a PaaS that quickly deploys containers to global edge locations. Internally it converts container images into lightweight Firecracker microVMs.

The single phrase "deploy on AWS" hides choices that span very different abstraction levels. From managing one EC2 box directly all the way to function-level hosting like Lambda. Including other clouds and PaaS, the pic…

EC2 (Elastic Compute Cloud) is the first compute service AWS released, and it popularized the cloud "virtual machine" abstraction. As managed services have grown, the share of direct usage has diversified, but EC2 remai…

AWS network firewalling has two layers: the Security Group (SG) attached to instances, and the Network ACL (NACL) attached to subnets. The names are similar, but the operating models differ quite a bit.

Whether a subnet is "public" or "private" is decided by routing, not by labels. Once we understand how Internet Gateway (IGW), NAT Gateway, route tables, and VPC endpoints combine, the meaning of subnet design becomes c…

A VPC (Virtual Private Cloud) is the virtual network where compute, databases, and load balancers live in AWS. If the shape of the VPC is not defined first, every decision inside it stays unstable.

AWS effectively defined the cloud services market. The service catalog tops 200, but at the category level it boils down to a handful of larger groupings.

Making data is not a backup. Restoring is. The difference only shows up after an incident. Here is a summary of PostgreSQL's tools, policies, and rehearsals.

Code that handles images shows up often. Resize an uploaded photo, convert formats, generate thumbnails.

To deliver messages on mobile or web while the app is closed, the push channels provided by the OS or the browser must be traversed. iOS has APNs, Android has FCM, and the web has the Web Push standard.

Supabase emerged as an alternative to Firebase, an open-source backend bundle. PostgreSQL sits at the core, with auth, storage, realtime, and serverless functions stacked around it.

The trend of combining large language model responses with external knowledge has settled under the name RAG (Retrieval-Augmented Generation). At its core sits vector similarity search, and PostgreSQL's pgvector extensi…

Kafka is often called a "queue," but more precisely it is a distributed commit log. Its strengths show beyond queues. At the same time, it is overkill for a simple work queue.

Systems that handle external data reduce to similar steps everywhere. Fetch the data, clean it, store it, and expose it.

Redis started as an in-memory key-value store, but today it covers cache, sessions, queues, ranking, distributed locks, and pub/sub all at once.

Cache rarely sits in only one place. It usually stacks across several layers. Closer to the client is faster; closer to the DB is more accurate.

The longer we use PostgreSQL, the more we run into a few concepts at least once: MVCC, indexes, EXPLAIN, isolation levels, VACUUM, partitioning.

Choosing a data store is often a burden. NoSQL, distributed SQL, graph DBs, time-series DBs all line up. Yet for many projects, PostgreSQL alone is enough for a long time at the start.