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!
📍London, Old Street | 🏢 2 Days in Office
Database Engineering at Capital on Tap 🌞
Our platform runs on .NET and SQL Server on Azure, and it has grown a long way past what it was originally designed for. We are hiring our first dedicated database performance engineer to own performance and scale: to make the fast paths fast, to keep them fast as volume grows, and to give every engineer here the tooling and the judgement to write data access that holds up in production. You will join a small agile team comprising DBAs and site reliability engineers in a hands-on senior individual contributor role. You will not be a ticket queue. You will pick the work that moves latency, cost and reliability, and you will be trusted to say 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.
Our Values & Culture
Just Pilot: We never settle for “good enough”. We pilot new ideas fast, ask questions to figure it out, and scale quickly.
Why Not Today? Fast is as slow as we go - speed and simplicity gives us a competitive advantage.
Be a Buddy: We tap in from day one to help the team, we do the right thing even if it’s hard.
Owners and Dates: We don’t chase people. If you own a task and agree to a date, the expectation is that it gets done.
Feedback: We want our employees to flourish, so we regularly provide direct and constructive feedback.
What We're Looking For 🔎
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.
Experience working with ORMs (ideally Entity Framework) and the particular performance tradeoffs that come with an ORM.
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.
Interview Process 🤝
30 minute screening with a talent partner
45 minute tech chat with Hiring Manager