what is scalability definition? - a system called scalable if it can meet increases in demand while remaining responsive. - a system may have to scale because of many reasons like increased data volume or increased amount of work, e.g., number of transactions. a scalable system would like to achieve scaling without performance loss. horizontal scaling horizontal scaling means that you scale by adding more servers into your pool of resources vertical scaling means that you scale by adding more power (CPU, RAM, Storage, etc.) to an existing server. horizontal scaling is often easier to scale dynamically by adding more machines into the existing pool; vertical scaling is usually limited to the capacity of a single server and scaling beyond that capacity often involves downtime and comes with an upper limit.

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