A Day in the Life: Jacob Selby, Site Reliability Engineer

1 August 2023 | Jacob Selby

After graduating from Leicester University with a Master’s in Physics, I found myself looking for a role which would enable me to apply the problem-solving skills I had developed during my degree. Whilst I wasn’t sure if I wanted to work as a Developer, I had always enjoyed coding work during my studies. So, when I came across the Site Reliability Engineer role at Luminance, I thought it aligned perfectly with my interest in computers, seeing code work in practice and problem-solving any hiccups along the way!

Here is a day in my life at Luminance…


We have a hybrid working model, meaning I go to Luminance’s office in Cambridge 3 days a week. As it’s Wednesday, I’m heading into the office today – I live only 25 minutes away, so I enjoy walking in when the weather is nice!


We kick off the morning with a team meeting. My team functions as part of the wider Operations team, and we are primarily responsible for maintaining platform consistency and acting as the first port of call if we encounter any errors. My day is typically split between resolving tickets – these are support queries submitted by customers – and proactively building solutions to prevent issues going forward. It’s always helpful to start the day by running through the top priority tickets and client feedback for the day so we’re up to speed on what needs doing.


We’re always trying to build up our tools and infrastructure, so we have designated ‘Improvements Time’. This is when we work on bigger projects that everyone in the team will benefit from, dedicating a few mornings per week to them. At the moment, we’re working to improve our internal monitoring; coming up with ways to get insight into our systems so that we can better predict when something may go wrong, or to get information as soon as possible when it does go wrong. This is the type of problem-solving I love in my role, as it requires me to constantly think of new ways to approach issues and find a logical solution. As part of this, I’ve been enjoying learning how to best use Prometheus query language to get data on key Site Reliability metrics.


After my morning meetings are complete, it’s coffee time – we have great fresh ground coffee in the office, along with some delicious vegan banana bread!

I then get to work on my Improvement Project. At the moment, I’m working on Alert Information Centralisation, which involves collating all the data from our different alerts into one database. Alerts are something we’ve configured ourselves to measure anything of importance to the team. An alert is triggered when a measured value exceeds a threshold we’ve determined. For example, if we measure that a site has been down for more than 5 minutes, we create a site down alert. We get the value using Prometheus, which runs a command and then exports the result as a metric. By collating this data into one database using PostreSQL, we’re aiming to conduct more comprehensive analysis and establish trends across all of our alerts.

This is a huge project so right now we’re planning out what each step will look like, from scraping information with Prometheus and Open Project’s API, to designing the Postgres schema our new centralised database will use. Most of these programmes were unfamiliar to me when I first started at Luminance, but I’ve been able to develop my skills and learn on the job with the support of my team.

Improvements time also gives us a chance to really dig deep into a project and learn the skills required to deliver it. Whilst I had a decent grasp of Python from my university studies, working with our ubuntu infrastructure has given me a crash course in bash, and I’m starting to get my head around the wonders of regex and vim.


Time for lunch – today, we have a few members of staff visiting from the London office, so we’re going to my favourite Japanese spot in Cambridge – Kineya Mugimaru. The Katsu Sweet Potato Curry is a favourite of mine and since the weather is nice, we’re enjoying it outside in the park. When the weather isn’t so good, we don’t mind sheltering in the office break room where we have a Nintendo Switch stocked up with games.


After lunch, we have another Support Consolidation Call. This is similar to the morning call but more forward-looking. Today, we’ve got a series of upgrades to run overnight. The delivery engineering team have recently released a new version of Luminance and some clients are eager to be upgraded overnight. This version makes some changes to the storage of data on how clients have tagged their documents. I need to write up a ticket for another member of the SRE team to add a new a task to our Ansible playbooks – to reformat existing document tags to fit this new format.


Now it’s time to work through some of the items on our list from Support. First up, they have passed me a ticket from a client with regards to document import failure. This looks like it’s a bug, so I work cross-functionally with Support to get a sample of the documents that the client is happy for us to inspect, and then with Dev to get the fix implemented on the client system.

The best part of my role is the satisfaction that comes with getting to the heart of an issue. I love not just solving new problems but also finding patterns in recurring problems to mitigate them going forward. For me, no two days are the same – if they are, there is something we could be doing better!


My after-work activities vary depending on the day. Often, I enjoy socialising with colleagues, especially on the first week after payday each month as we get free drinks! Tonight though, I’m making the most of the nice weather and going swimming.

Interested in finding out more about working at Luminance? Visit our careers page.