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Step by Step Guide on Setting Up Physical Streaming Replication in PostgreSQL

Physical streaming replication in PostgreSQL allows you to maintain a live copy of your database on a standby server, which continuously receives updates from the primary server’s WAL (Write-Ahead Log). This standby (or hot standby) can handle read-only queries and be quickly promoted to primary in case of failover, providing high availability and disaster recovery. In this guide, I will walk through provisioning a primary PostgreSQL 16 server and a standby server on Linux, configuring them for streaming replication, and verifying that everything works. I assume you are an experienced engineer familiar with Linux, but new to PostgreSQL replication, so I will keep it friendly and straightforward. Figure: Real-time data streaming from a primary PostgreSQL server (left) to a standby server (right). The standby constantly applies WAL records received from the primary over a network connection, keeping an up-to-date copy of the database ready for failover. Step 1: Prepare Two Linux Servers and Install PostgreSQL 16 Before diving into PostgreSQL settings, set up two Linux servers (virtual or physical). One will act as the primary database server, and the other as the standby (read replica). For a smooth replication setup, both servers should be as similar as possible in OS, hardware, and PostgreSQL version. In particular, ensure the following prerequisites: PostgreSQL 16 is installed on both servers via the official PostgreSQL repositories. Both servers must run the same major PostgreSQL version and architecture (mixing different versions won’t work for physical replication). If you haven’t installed PostgreSQL yet, do so now (e.g., on Ubuntu: sudo apt install postgresql-16, or on RHEL/CentOS: use the PostgreSQL Yum repository). Make sure the PostgreSQL service is running on the primary server. Network connectivity: The standby must be able to reach the primary on the PostgreSQL port (default 5432). If the servers are in a cloud environment like AWS EC2, configure the security group or firewall to allow the standby’s IP to connect to the primary on port 5432. For example, in AWS you’d add an inbound rule permitting the standby’s private IP address (or subnet) access to port 5432 on the primary. It is best to use private network interfaces for replication to reduce latency and avoid exposing the database publicly. System settings: Ensure your servers have the necessary OS user and permissions for PostgreSQL. The installation usually creates a postgres UNIX user that owns the data directories. You will run many commands as this postgres user. Also, verify that important prerequisites like consistent time sync (NTP) are in place, as it is generally good practice for database servers (though not specific to replication). With the infrastructure ready, let’s proceed to configure the primary PostgreSQL server to accept replication connections.
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Improving PostgreSQL Performance with Partitioning

My recommended methodology for performance improvement of PostgreSQL starts with query optimization. The second step is architectural improvements, part of which is the partitioning of large tables. Partitioning in PostgreSQL is one of those advanced features that can be a powerful performance booster. If your PostgreSQL tables are becoming very large and sluggish, partitioning might be the cure. The Big Table Problem Large tables tend to grow uncontrollably, especially in OLTP or time-series workloads. As millions or billions of rows accumulate, you begin to notice: Slow queries due to full table scans or massive indexes. Heavy I/O usage, especially when indexes cannot fit in memory. Bloated memory during operations like sorting or joining. Increased maintenance cost, with longer VACUUM, ANALYZE, and REINDEX times. Hard-to-manage retention policies, as purging old rows becomes expensive. These problems are amplified in cloud-hosted databases, where every IOPS, GB, or CPU upgrade increases cost.
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SELECT FOR UPDATE – Reduce Contention and Avoid Deadlocks to Improve Performance in PostgreSQL

Relational databases are at the heart of countless applications around the world, from high-traffic e-commerce websites to enterprise resource planning (ERP) systems and financial services. Concurrency management—where multiple database transactions operate on the same data simultaneously—is critical to getting good performance and avoiding problems like deadlocks or data inconsistencies. When multiple transactions need to modify the same rows, ensuring data consistency can become tricky. A single wrong approach to locking can lead to suboptimal performance or even bring your application to a standstill as numerous transactions block one another. One tool in PostgreSQL’s arsenal to handle concurrency is SELECT FOR UPDATE. It allows you to lock specific rows before updating them, preventing other transactions from modifying those rows until your transaction completes. In this blog, we will dive deep into SELECT FOR UPDATE in PostgreSQL. We will explore how it helps in reducing contention, avoiding deadlocks, and ultimately boosting performance when dealing with highly concurrent applications.
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When HASH partitioning works better than RANGE

I have always been a fan of RANGE partitioning using a date/time value in PostgreSQL. This isn't always possible, however, and I recently came across a scenario where a table had grown large enough that it had to be partitioned, and the only reasonable key to use was a UUID styled identifier. The goal of this post is to highlight when and why hashing your data across partitions in PostgreSQL might be a better approach. Range vs. Hash Partitioning in PostgreSQL Range Partitioning (A Quick Recap) Range partitioning in PostgreSQL uses boundary values that define slices of the data, often by date or numeric ranges. If you have a transactions table, you might create monthly partitions based on a transaction_date column. This is intuitive for time-series data because each partition holds rows from a specific date range. Advantages of Range Partitioning: Easy pruning for date-based queries. Straightforward approach to archiving old data: drop an entire partition for a past month, rather than issuing a massive DELETE. Pairs nicely with time-based ingestion pipelines, where every day or month gets its own partition. But as convenient as that is, there are cases where range partitioning runs into problems. Why Range Partitioning Can Fall Short Data Skew: If a huge portion of data lands in a single time interval—say, because of a traffic spike in the current month—that monthly partition might end up significantly larger than the others. Complex Backfills: Not everyone ingests data in an orderly, daily manner. Sometimes you need to re-ingest or correct data that spans multiple periods. Merging or splitting range partitions can get cumbersome. Non-Date Dimensions: Some tables aren’t naturally tied to a sequential numeric or date dimension. If your queries center on user IDs or device IDs, dividing by date might not solve your performance issues.
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Leveraging autovacuum in PostgreSQL to optimize performance and reduce costs

Autovacuum is one of PostgreSQL's most powerful features, designed to maintain database health and optimize performance by automating routine maintenance tasks. However, improper configuration can lead to performance bottlenecks, excessive costs due to resource inefficiency, or uncontrolled table bloat. This blog explores what autovacuum is, its role in performance optimization and cost reduction, and best practices for configuring its parameters. What is Autovacuum? Autovacuum is a background process in PostgreSQL responsible for maintaining table health by performing two critical tasks: 1. Vacuuming - Removes dead tuples (rows that have been updated or deleted but are no longer visible). - Frees up space for reuse to prevent table bloat and reduce storage costs. 2. Analyzing - Updates table statistics used by the query planner to optimize execution plans, improving query performance. Without autovacuum, dead tuples can accumulate, leading to: - Table Bloat: Increased disk usage drives up storage costs and slows query performance. - Transaction ID Wraparound: A situation that forces the system to go into ‘safe mode’, blocking non-superuser transactions to protect data integrity. This can render the database unusable if not addressed, causing downtime and increased operational costs. By automating these tasks, autovacuum ensures consistent database performance and minimizes unnecessary costs.
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Cut Cloud Costs with Smarter PostgreSQL CPU Core Allocation

Cloud costs can quickly spiral out of control if resources are not optimized. One of the most significant contributors to these costs is CPU core allocation, which forms the basis of the instance size with every major cloud provider. Many organizations over-provision cores for their PostgreSQL databases, paying for unused capacity, or under-provision them, leading to poor performance and missed SLAs. This blog will explore strategies to allocate CPU cores effectively for PostgreSQL databases, ensuring optimal performance while keeping cloud expenses in check. The Cost-Performance Tradeoff in the Cloud Cloud providers charge based on resource usage, and CPU cores are among the most expensive components. Allocating too many cores leads to wasted costs, while too few can cause performance bottlenecks. PostgreSQL databases are particularly sensitive to CPU allocation, as different workloads—OLTP (Online Transaction Processing) vs. OLAP (Online Analytical Processing)—place varying demands on processing power. Finding the right balance is essential to achieving both cost-efficiency and performance reliability. How CPU Core Allocation Impacts PostgreSQL PostgreSQL can leverage multi-core systems effectively, but how you allocate cores depends on your workload: - OLTP Workloads: High concurrency workloads benefit from multiple cores, allowing PostgreSQL to process many small transactions simultaneously. - OLAP Workloads: Analytical queries often rely on parallel execution, utilizing a few powerful cores to handle complex operations like aggregations and joins. Additionally, PostgreSQL supports parallel query execution, which can distribute certain operations across multiple cores. However, parallelism primarily benefits large analytical queries and can sometimes degrade performance for small or simple queries due to overhead. It is critical to assess your workload before over-allocating resources.
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Idle Transactions Cause Table Bloat? Wait, What?

Yup, you read it right. Idle transactions can cause massive table bloat that the vacuum process may not be able to address. Bloat causes degradation in performance and can keep encroaching disk space with dead tuples. This blog delves into how idle transactions cause table bloat, why this is problematic, and practical strategies to avoid it. What Is Table Bloat? Table bloat in PostgreSQL occurs when unused or outdated data, known as dead tuples, accumulates in tables and indexes. PostgreSQL uses a Multi-Version Concurrency Control (MVCC) mechanism to maintain data consistency. Each update or delete creates a new version of a row, leaving the old version behind until it is cleaned up by the autovacuum process or manual vacuuming. Bloat becomes problematic when these dead tuples pile up and are not removed, increasing the size of tables and indexes. The larger the table, the slower the queries, leading to degraded database performance and higher storage costs. How Idle Transactions Cause Table Bloat Idle transactions in PostgreSQL are sessions that are connected to the database but not actively issuing queries. There are two primary states of idle transactions: Idle: The connection is open, but no transaction is running. Idle in Transaction: A transaction has been opened (e.g., via BEGIN) but has neither been committed nor rolled back.
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VACUUM FULL in PostgreSQL – What you need to be mindful of

If you have worked with PostgreSQL for a while, you have probably come across the command VACUUM FULL. At first glance, it might seem like a silver bullet for reclaiming disk space and optimizing tables. After all, who would not want to tidy things up and make their database more efficient, right? But here is the thing: while VACUUM FULL can be useful in some situations, it is not the hero it might seem. In fact, it can cause more problems than it solves if you are not careful. Let us dive into: - What VACUUM FULL actually does - When you should use it - Why it is not the best solution for most cases - And what to do instead What Does VACUUM FULL Actually Do? PostgreSQL uses something called Multi-Version Concurrency Control (MVCC). Without getting too technical, MVCC keeps multiple versions of rows around to handle updates and deletes efficiently. These older versions of rows - called dead tuples - are cleaned up by a process called vacuuming. A regular VACUUM removes those dead tuples so the space can be reused. VACUUM FULL, however, goes further. It rewrites the entire table to remove dead space completely. It also rebuilds all the indexes on the table. Essentially, it is like dumping all your clothes out of the closet, refolding everything, and putting it back in neatly. Sounds great, right? So, why not use it all the time? When Should You Actually Use VACUUM FULL? There are a few very specific situations where VACUUM FULL makes sense: After Massive Deletions Imagine you delete millions of rows from a table. Regular vacuuming might not reclaim that disk space immediately, and the table could still look bloated. In this case, VACUUM FULL can shrink the table and give you that disk space back. Disk Space Crunch If your database server is running out of disk space and you need to reclaim it fast, VACUUM FULL can help (though it is still not ideal—more on that later). Post-Migration Cleanup If you have migrated a large table or reorganized your data, VACUUM FULL can clean things up during planned downtime. Outside of these scenarios, though, VACUUM FULL is usually not your best option. Why? Let us break it down.
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Understanding Wait Events in PostgreSQL

As databases grow in size and complexity, performance issues inevitably arise. Whether it is slow query execution, lock contention, or disk I/O bottlenecks, identifying the root cause of these issues is often the most challenging aspect of database management. One way to understand performance bottlenecks is to determine what the database is waiting for. Wait events in PostgreSQL provide detailed insights into what a database backend process is waiting for when it is not actively executing queries. Understanding and analyzing these events enables DBAs to resolve bottlenecks with precision. What Are Wait Events in PostgreSQL? Wait events represent the specific resources or conditions that a PostgreSQL backend process is waiting on while it is idle. When a process encounters a delay due to resource contention, input/output (I/O) operations, or other reasons, PostgreSQL logs the wait event to help you understand the source of the problem. Why Wait Events Matter Wait events can help reveal the underlying cause for slow query execution. For example: - When a query waits for a lock held by another transaction, it logs a Lock event. - When a process is waiting for disk reads, it logs an I/O event. - When a replication delay occurs, it logs a Replication event. By analyzing and acting on wait events, DBAs can: - Reduce query execution times. - Optimize hardware utilization. - Improve user experience by minimizing delays. How PostgreSQL Tracks Wait Events PostgreSQL backend processes constantly update their current state, including any associated wait events. These states are exposed through dynamic management views like pg_stat_activity and pg_stat_wait_events. By querying these views, you can see which events are impacting performance in real-time.
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3 Essential PostgreSQL Priorities for 2025

As IT budgets tighten and workloads increase, 2025 is the year to focus on maximizing PostgreSQL efficiency, security, and reliability. Whether you are running fully-managed or self-managed PostgreSQL databases, these three priorities - Reducing cloud costs - Increasing data security, and - Enhancing availability will be key to staying competitive. Here is a deep dive into each priority and actionable steps to make them a reality. 1. Reduce Cloud Costs Without Compromising Performance Cloud costs can escalate quickly when PostgreSQL instances are not optimized for the workload. Here is how to implement cost-saving measures with technical precision: Instance Sizing and Scaling Analyze Workload Patterns: Use tools like pg_stat_activity and pg_stat_user_tables to identify peak usage and idle times. Leverage this data to choose the right instance type and size. Autoscaling with Load Balancers: Deploy PostgreSQL in a cloud environment using managed services that support autoscaling or set up custom scaling policies. Storage and Index Optimization Partitioning: Use table partitioning to manage large datasets efficiently and reduce query processing times. For instance, partition large logs by time, and ensure that queries use partition pruning. Index Tuning: Remove redundant indexes using pg_stat_user_indexes and optimize index types (e.g., switching from B-Tree to GiST or GIN indexes for specific queries). This reduces storage requirements and speeds up query performance. Query Optimization EXPLAIN and ANALYZE: Run slow queries through EXPLAIN to pinpoint inefficiencies. Common culprits include sequential scans on large tables and ineffcient join strategies with large datasets. Caching Frequently Accessed Data: Use tools like pgpool-II to enable query result caching and connection pooling, minimizing redundant query execution. These optimizations not only reduce costs but also improve overall database responsiveness.
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