Staff Software Engineer, Run-Time Infrastructure - Slack

Slack enables people all over the world to communicate and collaborate together. Teams of all scales - from the world's largest public companies to the smallest of startups - use Slack to get work done, so we take performance and reliability very seriously.
A taste of our scale:

• The average user spends over 10 hours connected and 2.5 hours active in Slack every single day

• 1.5 billion+ messages are sent per month, half of those outside the United States

• Every day we see over 10M+ daily active users, over a billion web requests, and 10s of billions of database queries.

• We handle about 600k requests per second, summing up the entire day gets us at about 6 billion API requests served per day.

• For millions of people, Slack is the primary communication tool they use at work all day long. They expect it to be exceptionally reliable and fast, all the time.

About the team:

WebApp Infra (WIN) pillar provides the tools to make it possible for hundreds of developers to develop in a multi million line codebase with safety and productivity at the forefront. WIN handles maintenance and upgrades of the Hack programming language, static analysis tooling, widely used libraries in the codebase, asynchronous job queue, as well as tuning and debugging the HHVM runtime and other services it depends on. With four sub-teams : Language, Runtime, Reliability aka WIRE and asynchronous services (AServ), webapp infra team supports the middle layers of the stack above the AWS instances and below the product code. This role is open for the Runtime sub-team.

The WebApp Infra Runtime team is a small team making a large impact. We are responsible for Slack's deployment of HHVM, the virtual machine that runs the Hack programming language that Slack's Webapp backend is written in. We work with product teams to build Hack client libraries and C++ extensions to add more capabilities to WebApp. We fix bugs in HHVM and improve performance across the whole platform. Small improvements can make a big difference: every request that Slack's backend serves runs on systems we support.

We rapidly iterate and work closely with other teams in engineering to ensure we build resilient systems that can scale. We have a strong commitment to quality and understand that simplicity and reliability should be primary aspects of the systems that we build. We are ambitious, independent, and pragmatic.

What you will be doing:

• Collaborate with peers across Engineering to triage bugs and tackle sophisticated production issues across the stack, especially with respect to performance, memory, and stability
• Write, review, or provide feedback on a technical design proposal
• Maintain client libraries that allow backend engineers to access all the capabilities of the WebApp platform
• Test out a patch or new build of HHVM
• Upgrade the Hack language and HHVM runtime
• Optimize the build process or production HHVM configuration
• Make improvements to HHVM and potentially contribute them to the open-source project

What you should have:

• Degree or equivalent relevant experience required. Experience will be evaluated based on the core competencies for the role (e.g. extracurricular leadership roles, military experience, volunteer roles, work experience, etc.).
• Possess strong Computer Science fundamentals: data structures, algorithms, programming languages, operating system, distributed systems.
• Strong systems thinking abilities. You can reason about queues, retries, concurrency and contention and use them to build useful models of real software.
• Experience with Hack and HHVM (Hip Hop Virtual Machine), preferred Hack open source contributions
• Experience with Linux, including common debugging and profiling tools.
• Experience building large scale systems expertly for 5-7 years and can point to things you've worked on.
• Experience improving performance and reliability of a sophisticated system. You enjoy finding opportunities for performance and memory improvements through extensive profiling.
• Experience with Software-as-a-Service (SaaS). You have deployed plenty of code to live production environments, and understand what it takes to do so safely but efficiently.
• Can jump into situations with few guardrails and make things better.
• Write code that can be easily understood by others with an eye towards transparency and maintainability.
• Are a very strong communicator. You're excited to explain complex technical concepts and share your knowledge with different audiences.
• Are comfortable leading multi-functional projects and setting a vision for systems architecture.
• Are curious how things work and when things break you are eager and able to help fix them.
• Are comfortable mentoring and coaching engineers and sharing feedback.

Nice to have:

• Have experience working in large C++ codebases.
• Deep expertise in Hack and HHVM
• Have experience building, profiling, and debugging systems software, like language runtimes, databases, web servers, virtual machines and operating systems

Accommodations

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We warmly invite applications from individuals with a severe disability status (Schwerbehinderung). Salesforce is committed to equality and creating a workplace that reflects society. We set ambitious goals for representation, emphasize accessibility and inclusion, and continuously learn and improve. Learn more about our inclusion initiatives here (https://www.salesforce.com/company/accessibility/workplace-resources/#ally-sf-benefits). In 2019, Salesforce joined The Valuable 500 to champion disability inclusion in business leadership.

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