Senior Database Engineer

We’re Capital on Tap 👋
💳 Capital on Tap started because small businesses were underserved. Big banks were slow, their products weren't fit for purpose, and small business owners often couldn't access what they needed. We set out to fix that.
Today we're a financial platform - not just a credit card company. We offer a best-in-class business credit card, SME-focused spend management platform, a savings product that hit £1 billion in funds within its first year, and a growing suite of tools and financial products that make running a small business easier.
1,000+ employees, £20bn in annual card spend, 200,000+ customers, 17,000+ Trustpilot reviews averaging 4.7 stars, and we're profitable. We’ve done a pretty good job so far, but we’re just getting started!
🏡🏢This is a Hybrid role, the AI team work from our Moorgate (London) Offices 2 days per week.
The Role
Our platform runs on .NET and SQL Server on Azure, and it has grown well beyond what it was originally designed for. We're hiring our first dedicated Database Performance Engineer to own performance and scale: to make the fast paths fast, keep them fast as volume grows, and give every engineer here the tooling and judgement to write data access that holds up in production.
You'll join a small, agile team of DBAs and site reliability engineers in a hands-on, senior individual contributor role. You won't be working a ticket queue. You'll choose the work that moves the needle on latency, cost and reliability, and you'll be trusted to call out what needs re-architecting.
What You'll Do
Own query and index performance across our transactional SQL Server estate, using execution plans, Query Store, wait statistics, real production telemetry or other data driven measures.
Investigate and implement horizontal scaling techniques such as multi-cluster architecture, contained availability groups, sharding, etc, to ensure Capital on Tap’s distributed software estate can continue to support a fast growing customer base and increasing service count.
Find and remove the bottlenecks on our latency critical paths, starting with card authorisation and ledger read/writes, and hold them to an agreed p99 budget.
Own high availability and disaster recovery. Availability groups, failover, backup and restore testing against real RTO and RPO targets, and the runbooks that go with them.
Build and enhance self serve tooling to enable development teams to identify query plan regressions along with self service diagnostic tools to allow teams to debug their own query performance.
Automate what is currently manual, using PowerShell, Python, or Terraform, and treat database configuration as code.
Manage SQL Server cost as a first-class metric alongside latency and uptime.
Work alongside Product Engineering and our data analytics team, reviewing designs before they ship and levelling up how the whole engineering org thinks about data access.
Evangelise advanced database technologies to the software engineering teams. Research, demo and promote technologies such as graph databases and zero-downtime data migrations, and how they can be used in EF via C#.
What We're Looking For
Experience working with ORMs (ideally Entity Framework) and the particular performance tradeoffs that come with an ORM.
Substantial experience running Microsoft SQL Server in production at scale, whether that be self managed, Managed Instances, or on Azure SQL, in a business where downtime and latency have direct commercial impact.
Real depth in the internals. The query optimiser and plan cache, indexing and statistics, locking, blocking and isolation levels, tempdb, and the wait types that tell you which of those is actually hurting you.
A track record of specific, measurable performance wins you can walk us through end to end.
Experience scaling relational data past the point where tuning alone works. Partitioning, archival, denormalisation, caching, read replicas, or a considered move to a different store.
Comfortable writing application code, not just scripts. T-SQL to an expert level, plus PowerShell or Python, and infrastructure as code.
Hands-on with HA/DR design and with leading production incidents.
Working knowledge of other database engines such as PostgreSQL, and views on the relative pros/cons.
An ability to translate technical concepts and tradeoffs to non-database specialists.
Diversity & Inclusion 🌈
We welcome, consider and encourage applications from anyone who shares our commitment to inclusivity. Join us in creating a space where authenticity thrives, and everyone can do their best work.
Great Work Deserves Great Perks
We try not to take ourselves too seriously (all the time) so we make sure our office is decked out with a pool table, arcade machine, beer tap, and a couple of office dogs thrown in for good measure. Check out our benefits:
🏥 Private Healthcare including dental and opticians services through Vitality
✈️ Worldwide travel insurance through Vitality
🎁 Anniversary Rewards (£250, £500, £750, 4-week fully paid sabbatical)
👛 Salary Sacrifice Pension Scheme up to 7% match
🚘 Octopus EV Salary Sacrifice Scheme
🏖️ 28 days holiday (plus bank holidays)
📖 Annual Learning and Wellbeing Budget
👪 Enhanced Parental Leave
🚲 Cycle to Work Scheme
🚂 Season Ticket Loan
💬 6 free therapy sessions per year
🐶 Dog Frie