When designing a solution, what is the best use-case for Solid State Disk drives?

Big sequential writes (such as streaming or bulk data ingest) are a strength of high-capacity HDDs, which are more cost-effective per GB for large sequential workloads than SSDs.

Non-mission-critical environments do not justify the higher cost per GB of SSDs; HDDs are the cost-efficient choice where performance and reliability are less critical.

Backup-to-disk solutions prioritize high sequential throughput and low cost per GB, making large-capacity HDDs the appropriate and economical choice over SSDs.

SSDs have no mechanical parts, providing sub-millisecond latency and very high IOPS for random read/write operations. These characteristics make them ideal for mission-critical server applications and databases where response time and reliability are paramount, unlike HDDs which struggle with random I/O at scale.