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## Frequently Asked Questions

**Q. Why Tarantool?**

A. Tarantool is a result of a long trial and error process within Mail.Ru. It's the Nth generation of a family of custom in-memory data servers, developed for various web applications. Besides, when Tarantool development started (2008) there were no stable and sufficiently functional open source alternative.

** Q. Why Lua?**

A. Lua is a ligthweight, fast, extensible multi-paradigm language. Lua also
happens to be very easy to embed. Lua coroutines relate very closely to
Tarantool fibers, and Lua architecture works well with Tarantool internals. 
Lua is the first, but, hopefully, not the last stored program language for Tarantool.

**Q. What's the key advantage of Tarantool?**

A. Tarantool provides a fairly rich core feature set (HASH, TREE BITSET indexes, secondary indexes, composite indexes,
asynchronous replication, hot standby, data durability) along with support for Lua stored procedures.
These two properties make it possible to code fast, atomic and reliable in-memory data servers which handle non-trivial application-specific logic. The win over traditional SQL servers is in performance: low-overhead, lock-free architecture means Tarantool can serve
an order of magnitude more requests per second, on comparable hardware. The win over NoSQL alternatives is in flexibility: Lua allows flexible processing of data stored in a compact, denormalized format.

**Q. What are your development plans?**

A. They are standard. Performance. Better support for transactions. Master-master replication, automatic sharding.

**Q. Who is developing Tarantool?**

A. There is a small engineering team employed by Mail.ru -- check out our commit logs on github. The development is fully open, and most of the connectors authors and maintainers in different distributions are from the community.

**Q. How serious is Mail.Ru about Tarantool?**

A. Tarantool is an open source project, distributed under a BSD license, and as such does not depend on any one sponsor. However, it is currently and integral part of Mail.Ru backbone, so it gets a lot of support from Mail.ru.

**Q. Why is Tarantool primary port number 33013?**

A. It's a prime number which is easy to remember, because 3313, 3301, 313, 13 and 3 are also prime numbers.

**Q. My arena_used/items_used in SHOW SLAB output is >> 1. What does it mean and what should I do?**

A. If the ratio of arena_used to items_used >> 1, that indicates that there is fragmentation accumulated by the slab allocator. Imagine there are a lot of small tuples stored in the system initially, and later on each tuple becomes bigger and doesn't fit into its old slab size. The old slabs are never relinquished by the allocator. Currently this can be solved only by a server restart.

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