Viktar Patotski’s Blog

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.

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.

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.

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.

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.

Spring Boot 3 Migration Guide: javax to jakarta with OpenRewrite (and the sed Trap)

Sat, 26 Nov 2022 00:00:00 GMT

Migrate Spring Boot 2 to 3: the javax to jakarta package rename. Why the one-line sed trick quietly breaks javax.sql and javax.crypto, which packages actually move, and how OpenRewrite does the whole upgrade safely. 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 (List, Set, Map)

Tue, 23 Feb 2021 00:00:00 GMT

Inject every Spring bean implementing an interface into one field: a List or array (ordered with @Order), a Set, or a Map keyed by bean name. Working 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.