Viktar Patotski’s Blog

Build an MCP Server in Java with Spring AI: Give Your Product an AI Interface

Thu, 16 Jul 2026 00:00:00 GMT

On a well-built Spring Boot app, exposing your product to AI agents is almost trivial: annotate a service method, add one starter. The wiring is the easy part. Choosing what to expose and securing it is the real work. Here is the honest version, on Spring AI 2.0.

Database Encryption at Rest: What Protects You vs What Checks a Box

Mon, 13 Jul 2026 00:00:00 GMT

Turning on RDS encryption satisfies the compliance question and stops almost none of the attacks that actually leak data. Here is what each layer of encryption at rest really defends against, on Postgres and AWS, and how to build the one that protects the sensitive field.

RAG Explained: What It Is and When You Actually Need It

Mon, 13 Jul 2026 00:00:00 GMT

RAG means handing your AI the right page from your own documents before it answers. It is powerful when your knowledge base is large, changing, or per-customer. It is also something a lot of teams build too early. Here is the honest decision.

Secrets Management on AWS: Parameter Store vs Secrets Manager vs Vault

Mon, 13 Jul 2026 00:00:00 GMT

Environment variables are where secrets go to leak. Here is how to get them out, what each store actually buys you (and costs), and how to wire it into a Spring app without calling an API on every request.

Spring AI vs LangChain4j: Which Java AI Framework to Pick in 2026

Sun, 12 Jul 2026 00:00:00 GMT

You run a Java product and want to add an AI feature. There are two real framework choices. Here is the honest comparison across providers, RAG, tools, Spring fit, and the one thing that decides it for most teams.

Argon2 vs bcrypt vs scrypt: Which Password Hash to Use, and How to Tune It

Sat, 11 Jul 2026 00:00:00 GMT

The strength question first, then real numbers. Which password hashing algorithm actually protects you, what the current recommendations are, and how to tune each one to a verification time your login path can absorb.

Virtual Threads vs Platform Threads: A Spring Boot Benchmark on AWS

Thu, 09 Jul 2026 10:00:00 GMT

Do Java virtual threads make a Spring Boot app faster? I load-tested the same app both ways on real AWS hardware. The honest answer: below saturation they do nothing, on CPU-bound work they do nothing, and where they win on blocking I/O, a properly tuned platform pool matches the throughput. The real case for virtual threads is not raw speed, it is having no pool to tune and a cheaper thread.

Graviton vs Intel vs AMD: I Measured the Price-Performance on a Real Spring App

Thu, 09 Jul 2026 09:00:00 GMT

AWS says Graviton gives up to 40 percent better price-performance. I put the same Spring app on same-rank Intel, AMD, and Graviton instances and measured it. It is true, I got 43 to 60 percent, but the reason is not that Graviton is faster. It is cheaper, and same vCPU does not mean same cores.

Auditing Your Cloud and Identity Setup with AI

Tue, 07 Jul 2026 00:00:00 GMT

Most breaches are not a code bug. They are a public bucket or an over-broad role nobody reviewed. Here is how to use AI for an expert first pass over your cloud, identity, and infrastructure config, and the tools and guardrails that keep it honest.

What an LLM Feature Really Costs

Tue, 07 Jul 2026 00:00:00 GMT

The API price page says a few dollars per million tokens and looks cheap. That is not what your AI feature will cost. Here is the real formula, a worked example, the levers that cut the bill, and when self-hosting actually pays.

What Is Multi-Tenancy? A Plain-English Guide for SaaS Teams

Tue, 07 Jul 2026 00:00:00 GMT

Multi-tenancy means one running application serves many customers while keeping their data apart. Here is what it means, the apartment-building analogy that makes it click, the three models, and how tenants stay separated, with links to go deep on each.

Using AI for Secure Code Review: A Workflow That Holds Up

Mon, 06 Jul 2026 00:00:00 GMT

AI assistants can now scan your codebase for vulnerabilities and propose patches. Here is how to wire that into a real pipeline, why you still keep a deterministic scanner next to it, and the four places it will lie to you if you let it.

AI Wrote Your Code. It Wrote the Vulnerabilities Too.

Mon, 06 Jul 2026 00:00:00 GMT

Assistants like Copilot, Cursor, and Claude Code ship features fast and ship security holes at the same speed. Here are the flaws they reliably produce, with real before-and-after code, and how to use AI to catch them before an attacker does.

Tenant Data Isolation: It Is a Stack, Not a Switch

Mon, 06 Jul 2026 00:00:00 GMT

Row-Level Security is one layer, not the whole answer. Real tenant isolation is defense in depth across the data, the API, and the keys, so that no single mistake exposes another customer. Here are the layers and where each one earns its place.

Postgres Row-Level Security for Multi-Tenancy: The Pattern and the Footguns

Sun, 05 Jul 2026 00:00:00 GMT

Row-Level Security moves tenant isolation out of every developer's memory and into the database itself. Here is the exact Postgres pattern for a pooled multi-tenant app, plus the four footguns that leak data in production if you miss them.

How to Reduce Your AWS Costs: The Full Playbook

Sun, 05 Jul 2026 00:00:00 GMT

Most AWS bills carry 20 to 40 percent waste, and cutting it does not take a FinOps team. This is the whole method in four steps: see where the money goes, kill the waste, pay less for what remains, and keep the bill down for good. Each step links to its own deep dive.

Single-Tenant vs Multi-Tenant: The Decision Is Usually Both

Sat, 04 Jul 2026 00:00:00 GMT

The question is not which one wins, it is where you draw the isolation boundary. Here is how single and multi-tenant differ on cost, isolation, compliance, and ops, and why most SaaS that scales ends up running both at once.

Multi-Tenant Architecture for Vertical SaaS: Pick the Model on Purpose

Fri, 03 Jul 2026 00:00:00 GMT

Silo, pool, or bridge is one of the few architecture choices you cannot cheaply reverse. Here are the three models in plain terms, how they map to a real database, and a decision framework so you pick the one your customers and your margins actually need.

AWS Cost Explorer: How to Actually Read Your Bill

Thu, 02 Jul 2026 00:00:00 GMT

Your AWS bill is not a mystery, you just have not grouped it right. Cost Explorer is free and shows you where every dollar goes in about fifteen minutes. Here is the exact drill-down, which cost view to trust, and the one free alarm to set before you close the tab.

AWS Graviton: The 20% Cost Cut Most Teams Leave on the Table

Wed, 01 Jul 2026 00:00:00 GMT

Graviton instances cost up to 20% less than the x86 equivalent for the same work. On managed services it is a setting you flip. On your own compute it is a real migration with real gotchas. Here is which workloads move for free, which take effort, and which cannot move at all.

Amazon Aurora Cost: Where It Saves You and Where It Quietly Burns You

Tue, 30 Jun 2026 00:00:00 GMT

Aurora can be cheaper than RDS or twice the price, and the deciding line item is the one nobody watches: I/O. Here is how the bill is built, when I/O-Optimized and Serverless v2 actually save money, and the traps that turn a managed database into your biggest surprise.

AWS Savings Plans vs Reserved Instances: Which One Actually Cuts Your Bill

Mon, 29 Jun 2026 00:00:00 GMT

Both trade a commitment for a discount, but they are not interchangeable. Savings Plans buy flexibility, Reserved Instances buy the deepest rate, and the data tier plays by its own rules. Here is how to pick without locking up capital you will regret.

AWS Data Transfer Costs: Where the Money Leaks and How to Cut It

Sun, 28 Jun 2026 00:00:00 GMT

AWS charges to move bytes based on where they go. The expensive surprises are not the internet egress everyone expects, they are the cross-AZ chatter you cannot see. Here is the full rate ladder and the cheapest ways to cut the bill.

Database Optimization: Find the Bottleneck, Fix the Cheapest Thing First

Sun, 28 Jun 2026 00:00:00 GMT

Most database optimization guides hand you a list of ten techniques and skip the one question that matters: which problem do you actually have? Here is the diagnosis-first version. Find the real bottleneck, then apply the cheapest fix that clears it.

AWS NAT Gateway Pricing: The Hidden Cost Trap and How to Cut It

Sun, 28 Jun 2026 00:00:00 GMT

A NAT gateway charges you twice: an hourly fee per gateway and a per-GB processing fee on every byte through it, often on top of normal data transfer. Here is where the money leaks and the cheapest ways to stop it.

Redis Caching vs a Local In-Memory Cache: When You Actually Need the Network Hop

Wed, 24 Jun 2026 00:00:00 GMT

A cache is the reflex after you fix the slow query. The real decision is where it lives. A local in-memory cache is faster and simpler than Redis until you run more than one instance, and then it quietly serves stale data. Here is how to pick.

The Database Scaling Ladder: Every Cheaper Fix Before You Shard

Thu, 18 Jun 2026 00:00:00 GMT

Most teams reach for sharding years before they need it. There is a ladder of cheaper, lower-risk fixes that comes first, and the right rung depends on which bottleneck you actually have: read load, write load, or data size. Here is the ladder, from cheapest to last resort.

Postgres vs MySQL in 2026: Which to Pick for a SaaS (and When to Switch)

Wed, 17 Jun 2026 00:00:00 GMT

Both are excellent databases and for most SaaS workloads either one is fine. The honest answer: pick Postgres for greenfield, keep what you run well, and switch only for a reason you can name. Here are the few differences that actually decide it.

Database Indexes That Actually Help (and the Ones Quietly Hurting You)

Mon, 15 Jun 2026 00:00:00 GMT

Most slow-query problems are not a missing index, they are the wrong index, or ten indexes nobody needs. Start from the query plan, build the index the query actually wants, and drop the ones taxing every write.

Model Access Just Became a Supply-Chain Risk

Mon, 15 Jun 2026 00:00:00 GMT

A government directive can now switch off your AI provider overnight - and pricing, deprecation, and policy could always do it. If a core feature depends on one model API you don't control, that's a single point of failure. Here's how to treat model access like any other supply-chain risk.

How to Reduce AWS RDS Costs Without Hurting Performance

Sun, 14 Jun 2026 00:00:00 GMT

RDS is often the second or third biggest line on an AWS bill, sometimes the first, and most of it is avoidable. The levers that move it: fix the queries before you upsize, match the instance to your load shape, and stop provisioning storage for data that has not arrived yet.

The Business Case for Software Performance: Six Ways Speed Makes You Money

Thu, 11 Jun 2026 00:00:00 GMT

One product I worked on went from 8-second page loads to 500ms and conversion doubled. Performance is a P&L line. Here's the money math and what it means for SaaS.

Spring Boot on the JVM vs GraalVM Native: What Actually Wins on AWS

Wed, 27 May 2026 00:00:00 GMT

A head-to-head benchmark of the same Spring Boot app built for the JVM and as a GraalVM native binary - on real AWS hardware with a real database, run multiple times. Native wins startup, memory, and predictability; the warm JVM wins the median, peak throughput, and often the tail too - but the JVM swings run-to-run while native stays flat.

javax to jakarta: Migrate Spring Boot 2 to 3 the Safe Way

Sat, 26 Nov 2022 00:00:00 GMT

The javax to jakarta package rename is the hard part of the Spring Boot 3 upgrade. Why the one-line sed trick quietly breaks javax.sql and javax.crypto, which packages actually move, and how OpenRewrite does the whole migration for you. Tested on real apps.

Liquibase 'Could Not Acquire Change Log Lock' - Permanent Fix With Session Locks

Wed, 15 Jun 2022 00:00:00 GMT

Stop the recurring "could not acquire change log lock" error in Liquibase. Replace databasechangeloglock with Postgres session locks - auto-releases on connection drop, no manual unlock.

How To: Find top used shell commands (Linux, macOS)

Sat, 27 Feb 2021 00:00:00 GMT

How to find top used shell commands in Linux of macOS terminal.

Spring: Autowire All Beans of an Interface into a List, Set, or Map

Tue, 23 Feb 2021 00:00:00 GMT

How to inject every Spring bean that implements an interface into one field: a List or array (ordered with @Order), a Set, or a Map keyed by bean name. Working, copy-paste code for each.

Why should you write unit tests

Sat, 13 Feb 2021 00:00:00 GMT

Find reasoning and motivation to write unit tests for your application.

How To: Create a directory tree with a single command (Linux, macOS)

Wed, 03 Feb 2021 00:00:00 GMT

Create tree folder structure with a single command

Lombok @RequiredArgsConstructor: Spring Boot Constructor Injection

Sun, 31 Jan 2021 00:00:00 GMT

Constructor injection in Spring Boot with Lombok @RequiredArgsConstructor: drop @Autowired, keep fields final, no boilerplate. Setup with Maven and Gradle.