What interviewing.io does well
interviewing.io pairs you with a real engineer for an anonymous mock interview. Practicing with someone who has actually sat on the other side of the table is worth something no simulation fully replaces: they can riff on your answer and react in ways that are hard to predict.
Cost and how often you can practice
A single session on interviewing.io runs $150 to $225. 5 of them run $750 to $1125, which adds up fast if you want more than a session or two before the real thing.
CodeSparring's Pro plan costs $25 a month, or $225 billed yearly, and includes 100 AI interview sessions a month. That is enough sessions to make a mistake, fix it, and try again, without rationing every attempt.
When to use which
If you can afford a session or two on interviewing.io before an onsite, it is a strong way to get a read from someone who has been on the other side of a real loop. If what you need most is volume, practicing often enough that the format stops feeling new, that is where CodeSparring's session count earns its keep.
Plenty of candidates do both: CodeSparring for the bulk of the practice, then interviewing.io for a session close to the real thing.