https://wid-blog.github.io/en/categories/tech/Recent content in Tech on wid's blogHugoenSat, 09 May 2026 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/microservices-architecture/Sat, 09 May 2026 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/microservices-architecture/MSA is a decision about which criterion to use to decompose the system. Domain boundary, data ownership, scale pattern, failure isolation — the chosen criterion creates the service boundaries, and those boundaries decide communication and data in turn.https://wid-blog.github.io/en/posts/tech/architecture/event-sourcing-and-cqrs/Thu, 07 May 2026 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/event-sourcing-and-cqrs/ES and CQRS address how a system’s source of truth is shaped and how its views are separated from it. Adoption cost spreads across the system, so I lean toward adopting only when the value can be stated explicitly.https://wid-blog.github.io/en/posts/tech/architecture/distributed-transactions/Tue, 05 May 2026 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/distributed-transactions/Distributed transactions are about how a single ACID transaction decomposes across services and how its pieces are reassembled. The roles and trade-offs of 2PC, Saga (Choreography vs Orchestration), and Outbox.https://wid-blog.github.io/en/posts/tech/devenv/claude-code-config-layers/Fri, 01 May 2026 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/devenv/claude-code-config-layers/settings.json, CLAUDE.md, slash commands, subagents, hooks. Claude Code’s customization surface settles into four layers once you pick one axis: when does each one step in?https://wid-blog.github.io/en/posts/tech/devenv/macos-dev-environment/Thu, 30 Apr 2026 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/devenv/macos-dev-environment/alacritty + tmux + nvim + zsh + Claude Code in a single screen. The choices and structure behind a terminal-centric development environment.https://wid-blog.github.io/en/posts/tech/devenv/jira-sprint-workflow/Tue, 30 Dec 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/devenv/jira-sprint-workflow/Looking at JIRA’s issues and workflows as a graph of work units — covering the Sprint lifecycle, issue hierarchy, Git/GitHub integration patterns, and automation flows.https://wid-blog.github.io/en/posts/tech/devenv/github-actions-fundamentals/Mon, 15 Dec 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/devenv/github-actions-fundamentals/GitHub Actions seen as an event-driven automation engine — the three-layer abstraction of workflow / job / step, plus the operational details of triggers, runners, and secrets.https://wid-blog.github.io/en/posts/tech/devenv/github-pr-and-code-review/Sun, 30 Nov 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/devenv/github-pr-and-code-review/Looking at GitHub PRs as a collaboration layer on top of Git’s change graph, and walking through the Code Review cycle, PR-level design, and merge strategies.https://wid-blog.github.io/en/posts/tech/devenv/git-workflow-basics/Sat, 15 Nov 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/devenv/git-workflow-basics/Looking at Git as a graph of changes — and seeing how commit hygiene, branching strategy, and the merge-vs-rebase choice are all decisions about the shape of that graph.https://wid-blog.github.io/en/posts/tech/infra/vpc-security-fundamentals/Sat, 01 Nov 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/infra/vpc-security-fundamentals/How Security Groups (stateful, per-instance) and NACLs (stateless, per-subnet) form different layers of defense in a VPC, plus the common pitfalls each surface.https://wid-blog.github.io/en/posts/tech/infra/vpc-connectivity-fundamentals/Mon, 20 Oct 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/infra/vpc-connectivity-fundamentals/Comparing the four mechanisms that connect a VPC to other VPCs, on-premises networks, and external services — Peering, Transit Gateway, Site-to-Site VPN, and PrivateLink — across topology and cost.https://wid-blog.github.io/en/posts/tech/infra/vpc-routing-fundamentals/Wed, 01 Oct 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/infra/vpc-routing-fundamentals/How Route Tables decide traffic paths inside a VPC, the role of Internet Gateway and NAT Gateway as external exits, and the actual meaning of Public/Private Subnet.https://wid-blog.github.io/en/posts/tech/infra/vpc-isolation-fundamentals/Mon, 15 Sep 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/infra/vpc-isolation-fundamentals/How VPC simulates a private network boundary by combining IP CIDR, Subnet, and Tenancy. Includes vendor naming map across AWS / GCP / Azure / Alibaba.https://wid-blog.github.io/en/posts/tech/architecture/zero-downtime-data-transition/Tue, 15 Apr 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/zero-downtime-data-transition/A three-step pattern combining dual write and fallback read to transition data formats in live services without downtime.https://wid-blog.github.io/en/posts/tech/security/envelope-encryption/Tue, 01 Apr 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/security/envelope-encryption/How the CMK/DEK two-tier key structure in envelope encryption limits key leak impact and simplifies key rotation.https://wid-blog.github.io/en/posts/tech/ml/mlflow/Thu, 20 Feb 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/ml/mlflow/Which slot of the ML lifecycle each MLflow component fills, and which pieces a lightweight team can pick.https://wid-blog.github.io/en/posts/tech/design-pattern/circuit-breaker/Sat, 15 Feb 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/design-pattern/circuit-breaker/A Circuit Breaker’s trip trigger and recovery strategy must be designed together. Trip without recovery cuts the dependency permanently; recovery without a trip basis becomes meaningless cycling.https://wid-blog.github.io/en/posts/tech/design-pattern/rate-limiting/Fri, 14 Feb 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/design-pattern/rate-limiting/Before choosing a rate limit algorithm, the protection layer decides which algorithms are even available. This post lays out how L4/L7/Application layers and Token/Leaky/Sliding/Fixed algorithms intersect.https://wid-blog.github.io/en/posts/tech/ml/model-training-frameworks/Sat, 01 Feb 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/ml/model-training-frameworks/sklearn and ONNX aren’t competing at the same layer. Once you separate their roles, the real question becomes ‘do I need an ONNX layer at all?’https://wid-blog.github.io/en/posts/tech/ml/logistic-regression/Wed, 15 Jan 2025 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/ml/logistic-regression/The structure and characteristics of Logistic Regression, and why an old model still serves as the baseline in CTR prediction.https://wid-blog.github.io/en/posts/career/dable/campaign-cache-miss-retrospective/Wed, 27 Nov 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/career/dable/campaign-cache-miss-retrospective/The deploy was two days old, and the metrics had been calm the whole time. The moment we turned off the cache refresh batch, ad serving stopped. A retrospective on the missing verification of what a deploy actually changed.https://wid-blog.github.io/en/posts/tech/infra/kubernetes-fundamentals/Wed, 10 Apr 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/infra/kubernetes-fundamentals/Container orchestration basics and what backend developers need to know: core objects, networking, scaling with HPA, and operational essentials.https://wid-blog.github.io/en/posts/tech/language/go-concurrency-model/Fri, 05 Apr 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/language/go-concurrency-model/Go’s concurrency model builds on CSP, providing Goroutines and Channels as core tools. An overview of how each works and when to choose what.https://wid-blog.github.io/en/posts/tech/database/mongodb-vs-redis/Tue, 02 Apr 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/database/mongodb-vs-redis/Why MongoDB and Redis end up in different roles even under the same NoSQL umbrella. A comparison across data model, storage, schema, scaling, and use cases.https://wid-blog.github.io/en/posts/tech/language/spring-webflux-reactive-stack/Mon, 25 Mar 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/language/spring-webflux-reactive-stack/Spring MVC assigns one thread per request. When I/O waits pile up, threads sit idle. WebFlux replaces this with an event loop-based non-blocking model. A summary of the structural differences from MVC, the Reactor pattern, and when to choose which.https://wid-blog.github.io/en/posts/tech/network/http1-vs-http2/Wed, 20 Mar 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/network/http1-vs-http2/HTTP/1.1 processes requests and responses sequentially. HTTP/2 changed this with multiplexing, binary framing, and header compression. A summary of the differences between the two protocols and gRPC, which runs on top of HTTP/2.https://wid-blog.github.io/en/posts/tech/infra/docker-container-fundamentals/Fri, 15 Mar 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/infra/docker-container-fundamentals/Covers container concepts, the differences from VMs, Docker’s architecture, and the basics of Dockerfile and Docker Compose.https://wid-blog.github.io/en/posts/tech/architecture/horizontal-vertical-slicing/Sun, 10 Mar 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/horizontal-vertical-slicing/The difference between splitting code by technical layers (horizontal) and by features or domains (vertical). Trade-offs and selection criteria for each approach.https://wid-blog.github.io/en/posts/tech/language/nestjs-di-module-system/Mon, 26 Feb 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/language/nestjs-di-module-system/Nest.js provides a DI container and Module system at the framework level in the Node.js ecosystem. A summary of its core design principles: IoC, DI, Module, and Provider.https://wid-blog.github.io/en/posts/tech/architecture/layered-architecture/Fri, 23 Feb 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/layered-architecture/Layered architecture separates code into horizontal layers by technical responsibility. A summary of the four-layer structure, dependency direction rules, and how DIP decouples layers.https://wid-blog.github.io/en/posts/tech/infra/kafka-fundamentals-kraft/Thu, 22 Feb 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/infra/kafka-fundamentals-kraft/Core Kafka concepts (topics, partitions, consumer groups, replication) and the background behind KRaft mode, which removes the ZooKeeper dependency.https://wid-blog.github.io/en/posts/tech/architecture/go-hexagonal-architecture/Wed, 21 Feb 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/go-hexagonal-architecture/Core concepts of Hexagonal Architecture and its idiomatic implementation in Go using implicit interfaces and package structure for dependency direction control.https://wid-blog.github.io/en/posts/tech/design-pattern/builder/Sun, 11 Feb 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/design-pattern/builder/Builder is the answer when three limits of constructors meet at once — many parameters, some optional, and step-wise validation. With fewer than all three, simpler tools suffice. When the language provides rich named/default parameters, the need for Builder shrinks as well.https://wid-blog.github.io/en/posts/tech/design-pattern/factory/Sun, 04 Feb 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/design-pattern/factory/Factory’s shared intent is separating creation from use. The three variants — Factory Method, Abstract Factory, and Static Factory Method — split creation differently and suit different conditions. Static Factory Method is the variant most often encountered in practice, and DI containers absorb part of Factory’s explicit role.https://wid-blog.github.io/en/posts/tech/design-pattern/singleton/Sun, 28 Jan 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/design-pattern/singleton/Singleton is one of the simplest patterns but the canonical anti-pattern debate. The decision to bundle single-instance guarantee with global access into one pattern causes tight coupling and test difficulty. DI is the general alternative that separates the two intents.https://wid-blog.github.io/en/posts/tech/design-pattern/dependency-injection/Thu, 25 Jan 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/design-pattern/dependency-injection/DIP (principle), IoC (pattern), and DI (technique) sit at different levels of abstraction. The hierarchy must be clear before framework features and design principles can be told apart.https://wid-blog.github.io/en/posts/tech/architecture/incremental-cache-refresh/Sat, 20 Jan 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/architecture/incremental-cache-refresh/A pattern for switching from full cache refresh to incremental refresh. Separating data by update frequency and applying change detection reduces network costs.https://wid-blog.github.io/en/posts/career/dable/ad-campaign-cache-optimization/Mon, 15 Jan 2024 00:00:00 +0000https://wid-blog.github.io/en/posts/career/dable/ad-campaign-cache-optimization/How I reduced network costs and enabled instance downscaling by switching from full cache refresh to incremental refresh for campaign configuration data.https://wid-blog.github.io/en/posts/tech/database/rdb-transaction-acid/Fri, 01 Sep 2023 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/database/rdb-transaction-acid/What each of the four ACID properties actually guarantees in an RDB transaction. A/C/D are relatively clear guarantees, but only I has ’levels’ — the gateway to the correctness vs. concurrency trade-off.https://wid-blog.github.io/en/posts/tech/network/tcp-udp/Tue, 01 Mar 2022 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/network/tcp-udp/Two transport protocols that backend developers encounter constantly. A summary of TCP and UDP — connection establishment, reliability guarantees, flow/congestion control mechanisms, and selection criteria.https://wid-blog.github.io/en/posts/tech/security/session-and-jwt/Sat, 20 Mar 2021 00:00:00 +0000https://wid-blog.github.io/en/posts/tech/security/session-and-jwt/HTTP is stateless. Maintaining user authentication requires storing state somewhere. This post covers the structure, trade-offs, and storage strategies of server-side sessions and client-side JWT tokens.