# Aurora MySQL database engine updates: 2016-11-10 (versions 1.9.0, 1.9.1) (Deprecated)
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**Version:** 1.9.0, 1.9.1

## New features
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+ **Improved index build** – The implementation for building secondary indexes now operates by building the index in a bottom-up fashion, which eliminates unnecessary page splits. This can reduce the time needed to create an index or rebuild a table by up to 75% (based on an `db.r3.8xlarge` DB instance class). This feature was in lab mode in Aurora MySQL version 1.7 and is enabled by default in Aurora version 1.9 and later. For information, see [ Amazon Aurora MySQL lab mode](https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraMySQL.Updates.LabMode.html) in the *Amazon Aurora User Guide*.
+ **Lock compression (lab mode)** – This implementation significantly reduces the amount of memory that lock manager consumes by up to 66%. Lock manager can acquire more row locks without encountering an out-of-memory exception. This feature is disabled by default and can be activated by enabling Aurora lab mode. For information, see [ Amazon Aurora MySQL lab mode](https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraMySQL.Updates.LabMode.html) in the *Amazon Aurora User Guide*.
+ **Performance schema** – Aurora MySQL now includes support for performance schema with minimal impact on performance. In our testing using SysBench, enabling performance schema could degrade MySQL performance by up to 60%.

  SysBench testing of an Aurora DB cluster showed an impact on performance that is 4x less than MySQL. Running the `db.r3.8xlarge` DB instance class resulted in 100K SQL writes/sec and over 550K SQL reads/sec, even with performance schema enabled.
+ **Hot row contention improvement** – This feature reduces CPU utilization and increases throughput when a small number of hot rows are accessed by a large number of connections. This feature also eliminates ` error 188` when there is hot row contention.
+ **Improved out-of-memory handling** – When non-essential, locking SQL statements are executed and the reserved memory pool is breached, Aurora forces rollback of those SQL statements. This feature frees memory and prevents engine crashes due to out-of-memory exceptions.
+ **Smart read selector** – This implementation improves read latency by choosing the optimal storage segment among different segments for every read, resulting in improved read throughput. SysBench testing has shown up to a 27% performance increase for write workloads .

## Improvements
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+ Fixed an issue where an Aurora Replica encounters a shared lock during engine start up.
+ Fixed a potential crash on an Aurora Replica when the read view pointer in the purge system is NULL.