Author needs to actually state what ECS is. From context I don't think he/she is referring to Amazon's Elastic Compute Service.
http://aras-p.info/texts/files/2018Academy%20-%20ECS-DoD.pdf
Unity's traditional entity system is suffering from a number of "OOP-isms" which make it hard/impossible to optimize for performance.
The new ECS strictly follows a Data-Oriented-Design approach, where everything is built around laying out the data in memory in a CPU-cache friendly way (and a few other things that neatly 'fall into place', like spreading work across CPU cores, a specialized 'high-performance' C# dialect, and the ability to move work from the CPU to the GPU).
The big question is how the traditional Unity audience will react, since the ECS programming model is quite a bit different from the old way, and it's no longer as simple to build a game from a jenga-tower of adhoc-hacks ;)
However, it's important to note that Unity is adding an ECS, not inventing the concept.
... which had some discussion earlier [1] and the top comment on that submission links to the article of this submission.
It's been well received so far (for example: https://forum.unity.com/threads/ecs-or-why-should-i-bother-m... ).
There's also a good incentive to adopt ECS for certain games; Unity is offering a hugely reduced runtime size if you follow the ECS pattern, which is much needed for web games and other “interactive experiences” (ads, mobile game demos). The “ECS for Small Things” presentation at GDC is worth a look for those interested:
What they are referring to as ECS is more than just composition over inheritance. There are entity component architectures that are just that--Unity's existing class based component architecture for example.
But the ECS in this case refers to Data Oriented Design--basically laying out data like normalized database tables. Every component system has a table, and each row in the table is the data for one component (you don't actually use a relational DB for this, the data is just organized in a similar manner). The entity itself is just an id that all of the components reference.
The concept as used in games started in the late 90s as Structs of Arrays instead of Arrays of Structs.
Here's a a good free book on the subject (there's a paid hard copy as well) http://www.dataorienteddesign.com/dodmain/
https://blog.therocode.net/2018/08/simplest-entity-component...