PostgreSQL High Availability on OCI: Why Your Failover Passes Every Test But Breaks in Production

If you have built PostgreSQL high availability clusters on AWS or Azure, you have probably gotten comfortable with how virtual IPs work. You assign a VIP, your failover tool moves it, and your application reconnects to the new primary. Clean. Simple. Done.Then you try the same thing on Oracle Cloud Infrastructure and something quietly goes wrong.The cluster promotes. Patroni (or repmgr, or whatever you are using) does its job. The standby becomes the new primary. But the VIP does not follow. Your application keeps sending traffic to the old node — the one that just failed. From the outside, it looks like the database is down. From the inside, everything looks green.
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Thinking of PostgreSQL High Availability as Layers

High availability for PostgreSQL is often treated as a single, big, dramatic decision: “Are we doing HA or not?”That framing pushes teams into two extremes:- a “hero architecture” that costs a lot and still feels tense to operate, or - a minimalistic architecture that everyone hopes will just keep running.A calmer way to design this is to treat HA and DR as layers. You start with a baseline, then add specific capabilities only when your RPO/RTO and budget justify them.Let us walk through the layers from “single primary” to “multi-site DR posture”.Start with outcomesBefore topology, align on three things:1. Failure scope a. A database host fails b. A zone or data center goes away c. A full region outage happens d. Human error2. RPO (Recovery Point Objective) a. We can tolerate up to 15 minutes of data loss b. We want close to zero3. RTO (Recovery Time Objective) a. We can be back in 30 minutes b. We want service back in under 2 minutesHere is my stance (and it saves money!): You get strong availability outcomes by layering in the right order.
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PostgreSQL Materialized Views: When Caching Your Query Results Makes Sense (And When It Doesn’t)

Your dashboard queries are timing out at 30 seconds. Your BI tool is showing spinners. Your users are refreshing the page, wondering if something's broken. You've indexed everything. You've tuned shared_buffers. You've rewritten the query three times. The problem isn't bad SQL - it's that you're forcing PostgreSQL to aggregate, join, and scan millions of rows every single time someone opens that report.
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PostgreSQL Column Limits

If you’ve ever had a deployment fail with “tables can have at most 1600 columns”, you already know this isn’t an academic limit. It shows up at the worst time: during a release, during a migration, or right when a customer escalation is already in flight. But here’s the more common reality: most teams never hit 1,600 columns; they hit the consequences of wide tables first
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PostgreSQL, MongoDB, and what “cannot scale” really means

Last week, I read The Register’s coverage of MongoDB CEO Chirantan “CJ” Desai telling analysts that a “super-high growth AI company … switched from PostgreSQL to MongoDB because PostgreSQL could not just scale.” I believe you can show the value of your own technology without tearing down another. That is really what this post is about.
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PostgreSQL License: Free to Use, Enterprise-Ready, and Cost-Efficient in Production

Do you need a PostgreSQL license for critical production use? Short answer: No. The open-source PostgreSQL database is free to download, use, modify, and distribute. There are no per-CPU, per-core, per-socket, or per-instance license fees. What you do need is a realistic plan for operational costs and expertise, the parts that make PostgreSQL truly production-grade. Many teams search for “PostgreSQL license” while budgeting for a new system or replacing proprietary databases. They want to know whether PostgreSQL is free like a hobby project or free like a platform you can trust with revenue. It is the latter - enterprise-reliable and secure, provided you run it with the right architecture and operational discipline.
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What Are “Dirty Pages” in PostgreSQL?

PostgreSQL stores data in fixed‑size blocks (pages), normally 8 KB. When a client updates or inserts data, PostgreSQL does not immediately write those changes to disk. Instead, it loads the affected page into shared memory (shared buffers), makes the modification there, and marks the page as dirty. A “dirty page” means the version of that page in memory is newer than the on‑disk copy.
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Configuring Linux Huge Pages for PostgreSQL

Huge pages are a Linux kernel feature that allocates larger memory pages (typically 2 MB or 1 GB instead of the normal 4 KB). PostgreSQL’s shared buffer pool and dynamic shared memory segments are often tens of gigabytes, and using huge pages reduces the number of pages the processor must manage. Fewer page‑table entries mean fewer translation‑lookaside‑buffer (TLB) misses and fewer page table walks, which reduces CPU overhead and improves query throughput and parallel query performance.
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