Mark Callaghan
Chief Technology Officer at Small Datum LLC
United States
Summary
🤩
Rockstar🎓
Top SchoolMark Callaghan is a veteran database architect and CTO with 19 years of experience designing and optimizing storage and transaction systems at companies like Facebook, Google, MongoDB and Oracle. He specializes in open-source database engines—MySQL, Postgres and RocksDB—and has driven web-scale innovations such as InnoDB compression, replication improvements, group commit and extensive performance tuning. As founder of Small Datum LLC he consults on high-performance storage and is an active contributor to prominent projects like RocksDB and the sysbench benchmark, where his changes improved compression configuration, compaction behavior and realistic workload testing. His career blends low-level C systems work with large-scale operational experience supporting clusters with hundreds of millions of queries per second, and he frequently publishes practical notes and tools that influence production deployments. Known for pragmatic performance engineering, he pairs academic credentials (MS Computer Science, UW–Madison) with a rare depth in both database internals and benchmarking.
18 years of coding experience
27 years of employment as a software developer
MS, Computer Science, MS, Computer Science at University of Wisconsin-MadisonBS, Computer Science, BS, Computer Science at San Diego State UniversityComputer Science, Computer Science at Rutgers University
Github Skills (21)
benchmark10
c-language10
mysql10
rocksdb10
query-optimization10
benchmarking10
c1110
c1710
database-tuning10
cprogramming-language10
database-optimization10
optimization10
postgresql9
command-line-interface9
data-structures8
Programming languages (9)
Github contributions (5)
facebook/rocksdb
Sep 2012 - Oct 2022
A library that provides an embeddable, persistent key-value store for fast storage.
Role in this project:
Back-end Developer & Performance Engineer
Back-end Developer & Performance EngineerContributions:20 reviews, 79 commits, 27 PRs in 10 years 2 months
Contributions summary:Mark primarily contributed to the performance optimization of the RocksDB database. They added options to configure compression algorithms and compression levels within the `db_bench` benchmark tool. The user also removed the use of mmap for random reads and added statistics to improve the analysis of the code. Furthermore, they have made changes to rate-limit write operations to ensure that compactions do not get starved, which leads to better read performance.
persistent-storagebigtablefast-storagelsm-treedatabase
akopytov/sysbench
Sep 2009 - Oct 2016
Scriptable database and system performance benchmark
Role in this project:Back-end Developer & Database Engineer
Back-end Developer & Database EngineerContributions:14 commits, 3 PRs, 3 comments in 7 years 1 month
Contributions summary:Mark primarily contributed to enhancing the `sysbench` project's database performance testing capabilities. They added new command-line options related to random number generation seeding and using MySQL HANDLER statements for point selects. Their work involved modifying core C code, including the addition of new arguments, conditional logic, and database query modifications, suggesting a focus on optimizing and expanding database testing features. They also introduced options to influence the test behavior, such as using secondary indexes.
benchmarkfreebsdmicro-benchmarksdatabasepostgresql
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