You can choose between M6g and R6g instance families and three database engines (MySQL 8.0.17 and higher, MariaDB 10.4.13 and higher, and PostgreSQL 12.3 and higher).
官方宣稱可以提供 35% 的效能提昇，考慮費用的部份會有 52% 的 c/p 值提昇：
Graviton2 instances provide up to 35% performance improvement and up to 52% price-performance improvement for RDS open source databases, based on internal testing of workloads with varying characteristics of compute and memory requirements.
對於 RDS 這種純粹就是個服務的應用來說，感覺應該不會有什麼轉移成本，只要測過沒問題，換過去等於就是現賺的。看起來等 RI 約滿了就可以切...
January 14, 2020 – Instances created on or after this date will have the new (CA-2019) certificates. You can temporarily revert to the old certificates if necessary.
Amazon RDS Proxy supports Amazon RDS for MySQL and Amazon Aurora with MySQL compatibility, with support for additional RDS database engines coming soon.
定價策略看起來是依照後端資料庫的 vCPU 計算：
Pricing is simple and predictable: you pay per vCPU of the database instance for which the proxy is enabled.
Amazon RDS Proxy is available in preview for RDS MySQL and Aurora MySQL in US East (N. Virginia), US East (Ohio), US West (Oregon), EU West (Ireland), and Asia Pacific (Tokyo) regions. Support for RDS PostgreSQL and Aurora PostgreSQL is coming soon.
看起來 MySQL 系的 Global Database 就是跨區的 master-slave 架構 (所以標榜降低了 read latency，但沒有提到 write latency)：
An Amazon Aurora Global Database is a single database that spans multiple AWS regions, enabling low latency global reads and disaster recovery from region-wide outages.
另外可以看到是 1 秒，所以應該是 async replication：
Aurora Global Database replicates writes in the primary region with typical latency of <1 second to secondary regions, for low latency global reads.
然後可以跨區切換：
In disaster recovery situations, you can promote the secondary region to take full read-write responsibilities in under a minute.
We migrated 75 petabytes of internal data stored in nearly 7,500 Oracle databases to multiple AWS database services including Amazon DynamoDB, Amazon Aurora, Amazon Relational Database Service (RDS), and Amazon Redshift.
Cost Reduction – We reduced our database costs by over 60% on top of the heavily discounted rate we negotiated based on our scale. Customers regularly report cost savings of 90% by switching from Oracle to AWS.
More than 100 teams in Amazon’s Consumer business participated in the migration effort.
My experience is in web- sites/apps/services. From tiny personal projects to commercial apps running on 8,000 servers. If what you do is AI, ML, ETL, HPC, DBs, blockchain, or anything significantly different from web apps, what I’m writing here might not be relevant.
另外從團隊的開發成本來看，這些 scale 的技術增加了開發成本，產生了很多開發上的限制，這些觀點也有點帶到「Premature optimization is the root of all evil」在講的事情：
Step 1: Forget that all these things exist: Microservices, Lambda, API Gateway, Containers, Kubernetes, Docker.
Anything whose main value proposition is about “ability to scale” will likely trade off your “ability to be agile & survive”. That’s rarely a good trade off.
Conclusion: I like to seperate interesting new tech from tech that has survived the test of time. EC2, S3, RDS, DDB, ELB, EBS, SQS definitely have. If you’re considering alternatives, there should be a strong compelling reason for losing all the benefits accrued over time.
