Cassandra Database Engineer - NoSQL in London

Duration: Up until 31 March 2026 (Possibility for extension)

Location: London/Hybrid (3 days per week on site)

Rate: A highly competitive Umbrella Day Rate is available for suitable candidates

Role Purpose

The Financial Crime Technology team requires specialist Apache Cassandra (NoSQL) expertise to support the design and operational readiness of high-volume, real-time data platforms underpinning the fraud detection ecosystem. This capability does not currently exist in-house, as the team's core expertise is centred on Actimize application engineering, Oracle PL/SQL, and integration middleware (IIB/MQ). This is a time-bound requirement aligned to specific deliverables, including the real-time payment capture and replay platform and its supporting data infrastructure, rather than a permanent headcount need. As such, a contract engagement is the most appropriate and cost-effective resourcing model. Without this role, delivery timelines are at risk, and critical design decisions (such as keyspace design, replication strategy, and capacity planning) may be made without specialist input, increasing the risk of rework and potential production instability.

Key Accountabilities:

• Design, implement and maintain Apache Cassandra clusters, including keyspace design, replication strategies and partitioning models.
• Develop and optimise data models aligned to query patterns (denormalization, partition key design, avoiding hotspots and wide partitions).
• Performance tuning: compaction strategies consistency levels, read/write path optimisation, JVM/GC tuning.
• Manage cluster operations: node additions/decommissions, repairs (node tool), backups and disaster recovery.
• Monitor cluster health using tools such as Prometheus/Grafana, OpsCenter, or equivalent.
• Support CQL query development and advise application teams on best-practice access patterns.
• Collaborate with infrastructure and security teams on hardening, encryption (at rest/in transit) and authentication/authorisation (RBAC).
• Produce technical documentation including data models, runbooks, and operational procedures.

Knowledge & Experience:

• Degree in Engineering, Computer Science, Business Administration, or a related field.
• Proven experience in NoSQL database engineering, with strong production expertise in Apache Cassandra.
• Strong proficiency in keyspace and table design, data modelling aligned to query patterns, replication strategy, and consistency tuning.
• Solid CQL experience and good understanding of Cassandra internals (SSTables, memtables, commit log, compaction, gossip, tombstones).
• Hands-on experience with cluster operations including node additions/decommissions, repairs, backups, and disaster recovery (node tool).
• Experience with cluster sizing, capacity planning, and multi deployments.
• Strong Linux administration and scripting skills (Bash/Python).
• Experience working in regulated or financial services environments with awareness of security hardening, encryption (at rest/in transit) and RBAC.
• Exposure to the Actimize platform, messaging middleware (IBM MQ/IIB, Kafka). Or Oracle Pl/SQL desirable but not mandatory.
• DataStax/Cassandra certification and cloud experience (AWS Keyspaces, Azure Managed Instance for Cassandra) desirable.
• Experience working in Agile delivery environments, contributing to ceremonies and cross-functional collaboration.
• Demonstrated accountability in managing services, resolving issues, and coordinating stakeholders across teams or regions.

Candidates will need to show evidence of the above in their CV in order to be considered.

If you feel you have the skills and experience and want to hear more about this role 'apply now' to declare your interest in this opportunity with our client. Your application will be observed by our dedicated team. We will respond to all successful applicants ASAP however, please be advised that we will always look to contact you further from this time should we need further applicants or if other opportunities arise relevant to your skillset.

Pontoon is an employment consultancy. We put expertise, energy, and enthusiasm into improving everyone's chance of being part of the workplace. We respect and appreciate people of all ethnicities, generations, religious beliefs, sexual orientations, gender identities, and more. We do this by showcasing their talents, skills, and unique experience in an inclusive environment that helps them thrive.

As part of our standard hiring process to manage risk, please note background screening checks will be conducted on all hires before commencing employment. We use generative AI tools to support our candidate screening process. This helps us ensure a fair, consistent, and efficient experience for all applicants. Rest assured, all final decisions are made by our hiring team, and your application will be reviewed with care and attention.