Great question—let’s break down the practical pros and cons of each option, plus clear scenarios where Aurora makes more sense than standard RDS for PostgreSQL or MySQL workloads.

Aurora PostgreSQL/MySQL: What It Does Better #

• Blazing-fast performance & scalability: Unlike RDS, which uses attached EBS volumes, Aurora runs on a distributed, auto-scaling storage layer that grows up to 128TB per instance without manual intervention. It delivers up to 5x faster throughput than RDS MySQL and 3x faster than RDS PostgreSQL for most workloads, thanks to optimized I/O paths and reduced overhead. For read-heavy apps, you can spin up 15 Aurora Replicas (vs. 5 for RDS) with sub-10ms replication lag—perfect for offloading traffic from your primary instance.
• Next-level availability & durability: Aurora replicates your data across 3 AZs by default (same as multi-AZ RDS, but with finer-grained, continuous replication). Failover to a replica typically takes under 30 seconds (compared to 60-120 seconds for RDS multi-AZ), which is critical for apps that can’t tolerate downtime. Data is also backed up to S3 with 6 copies across 3 AZs, giving you 99.999% durability—meaning you’re extremely unlikely to lose data.
• Cost efficiency at scale: While Aurora’s base instance cost is higher than RDS, its storage pricing model is more flexible. You pay per GB used, and Aurora Auto Scaling IOPS eliminates over-provisioning costs for variable workloads. For apps with spiky traffic, Aurora Serverless v2 auto-scales compute capacity in milliseconds, so you only pay for what you use during peaks—no wasting money on idle resources.
• Unique advanced features: Aurora has tools you won’t find in standard RDS, like:
  • Global Database: Cross-region replication with <1s lag for disaster recovery or global user bases
  • Aurora Backtrack: Restore your database to any point in time (up to 72 hours) without restoring from a backup
  • Lambda integration: Trigger serverless functions automatically when data changes (e.g., syncing to a data warehouse)

RDS PostgreSQL/MySQL: Where It Shines #

• Lower upfront cost for small workloads: If you’re running a small app, legacy system, or low-traffic database, RDS is cheaper out the door. Its base instance pricing is lower, and for predictable, low-I/O workloads, provisioned IOPS on RDS can be more cost-effective than Aurora’s storage model.
• Simpler management for basic use cases: RDS is straightforward—no need to wrap your head around Aurora’s distributed storage layer. It’s a great fit for teams that don’t need advanced features and just want a reliable, easy-to-manage managed database.
• Wider instance type support: RDS offers more instance families, including burstable t2/t3 instances that are perfect for low-traffic apps or development environments. Some older or specialized instance types are only available in RDS, so if you have specific hardware needs, it might be the only option.
• 100% compatibility & familiarity: RDS is a traditional managed database that’s fully compatible with standard PostgreSQL/MySQL. Most DBAs already know how to manage RDS backups, restores, and parameter groups, so migrating from on-prem or other managed databases is seamless—no code changes required.

When to Choose Aurora Over RDS #

• You have read-heavy or high-concurrency workloads: E-commerce platforms, analytics dashboards, or SaaS apps with thousands of concurrent users will benefit from Aurora’s fast replication and multiple read replicas.
• Downtime is not an option: If your app is in a regulated industry (like finance) or requires real-time availability, Aurora’s sub-30s failover and global database capabilities are non-negotiable.
• Your traffic is unpredictable: Aurora Serverless v2 is ideal for seasonal apps, startups with growing user bases, or any workload where traffic spikes and drops dramatically—you’ll save money by only paying for compute when you need it.
• You need advanced features: If you require cross-region replication, backtrack, or event-driven workflows with Lambda, Aurora is the only managed PostgreSQL/MySQL option in AWS that offers these tools.
• Your database is scaling beyond a few TB: As your database grows, Aurora’s auto-scaling storage and pay-per-use model becomes more cost-effective than RDS’s provisioned IOPS, which can get prohibitively expensive at scale.

内容的提问来源于stack exchange，提问作者Shruti