Senior Software Engineer (Database Reliability)

Capitalontap; Greater London; Hybrid; GBP 85,000 - 130,000; Full time

Benefits offered by this job

Private Healthcare including dental

Worldwide travel insurance

Salary Sacrifice Pension Scheme

28 days holiday

Wellbeing budget

Job summary

Capital on Tap is hiring a Database Performance Engineer to own performance and scale for a fast-growing financial platform. You will work in a small, senior team to optimize latency, cost and reliability in a hybrid London office.

You will lead database query optimisation, explore new technologies, and ensure high availability across Azure SQL Server estates, while enabling product engineering with strong data access practices.

Qualifications

• Experience with ORM technologies and the performance tradeoffs of ORMs.
• Production-grade SQL Server in production at scale with low downtime.
• Deep understanding of query optimisation, indexing, statistics, locking and wait types.

Responsibilities

• Evangelise advanced database technologies to engineering teams.
• Own query and index performance across SQL Server estate.
• Investigate and implement horizontal scaling techniques for distributed software estate.
• Identify bottlenecks in latency-critical paths and enforce p99 budgets.
• Own high availability and disaster recovery planning and testing.
• Create self-serve tooling for query plan regression detection and diagnostics.
• Automate tasks using PowerShell or Terraform and treat DB configuration as code.
• Manage SQL Server cost as a key metric alongside latency and uptime.
• Collaborate with data analytics to shape data access designs.

Skills

Entity Framework

SQL Server

T-SQL

PowerShell

Infrastructure as Code

Education

Bachelor's degree in Computer Science or equivalent

Tools

Azure SQL

Query Store

SQL Server

Job description

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 Database 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 Database Engineers 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

• 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#.
• 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 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.

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, 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.

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 BudgetEnhanced Parental Leave
• Cycle to Work Scheme
• Season Ticket Loan
• 6 free therapy sessions per year
• Dog Friendly Offices
• Free drinks and snacks in our offices

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