This role has closed 1w ago. It is no longer on Twitter's board, so there is nothing left to apply to. The posting is kept here because you saved it or opened it; it is a record, not an offer.

Verified by our engine · Posted +6mo ago

Twitter

Software Engineer, Sandbox Service

Twitter · Infrastructure

London

Mid-level

SoftwareC++LinuxPythonRust

Last seen 1w ago

Posted
+6mo ago

Posted on 18 December 2025

Workplace
Not specified

Work model not stated

Salary
£107k – £262k

Range published by Twitter

Visa sponsorship
Not specified

Visa sponsorship details unknown

This role has closed. It's kept as a record — see Twitter's open roles or the similar live roles below.

See Twitter's open roles

SpaceX was founded under the belief that a future where humanity is out exploring the stars is fundamentally more exciting than one where we are not. Today, SpaceX is actively developing the technologies to make this possible, with the ultimate goal of making life multiplanetary and expanding consciousness to the stars.

SpaceXSI is building Super Intelligence to help humanity understand the universe. Our teams are building the full Super Intelligence stack: from our Colossus supercomputers, to Grok models, to our suite of applications, including Grok Bot, Grok Build, Grok Imagine, Grok Voice, and X. We're creating a powerful flywheel where more compute trains better models, better models power more useful products, and what we learn from people using those products shapes what we build next.

SOFTWARE ENGINEER, SANDBOX SERVICE

The Sandbox service team at SpaceXSI builds and maintains a secure, scalable system that gives our models safe, controlled access to computational environments. This infrastructure powers critical workloads across training and product, enabling models to run code, build software, interact with tools, and even control applications with user interfaces. We provision containers and virtual machines on large-scale clusters, granting models interactive control over these remote environments. Our work spans the full stack: from orchestrating massive jobs and resource scheduling at the cluster level, to fine-tuning filesystem performance on nodes. The Sandbox service enables Grok to safely run and test code in real-time for user queries, and supports reinforcement learning in training, where models interactively explore tools ranging from compilers to productivity apps.

BASIC QUALIFICATIONS:

Experience with Rust, C++, or Go

Experience with virtualisation and containerisation technologies (e.g., cgroups, KVM, gVisor, QEMU)

PREFERRED SKILLS AND EXPERIENCE:

Solid knowledge of the networking stack

Familiarity with Python

Deep experience with either Linux or Windows systems (familiarity with both is a strong plus)

COMPENSATION AND BENEFITS:

£107,000 - £262,000 GBP

Base salary is just one part of our total rewards package at SpaceXSI, which also includes equity, comprehensive healthcare and dental coverage, cash plan, income protection, life insurance, and various other discounts and perks.

SpaceXSI is an equal opportunity employer. For details on data processing, view our Recruitment Privacy Notice.

About Twitter

X's (formerly Twitter's) European postings now route through xAI's own board and are concentrated in London and Dublin. Worth noting this is the merged X/xAI entity's hiring, not a standalone Twitter career site anymore.