As we now learn to live with COVID-19, the service is leaner and more efficient, with flexible products capable of supporting future home testing requirements to improve public health outcomes.

Here are our 6 key learnings since the service was first established:

In designing and developing the initial home testing service, we drastically shortened the Agile software development lifecycle from weeks to days. Getting the minimal viable product (MVP) live was key.

It went live on 24 April 2020, only a handful of days after work first started - a phenomenal achievement that meant keyworkers could order PCR tests to their homes to enable them to continue their critical work. We then iterated the service as necessary.

It was extended to other vulnerable user groups, including those who were 65 or over and referrals from NHS 111 Online, before being made available to the general public.

It was integrated with our wider platform for test site appointment bookings, meaning that people only had to enter their details once when choosing to either order a home test or book a physical test site appointment.

Elective care patient testing was added as a new use case, which enabled NHS trusts to order PCR tests to the homes of patients with an upcoming hospital procedure, helping to stop the spread of the virus in hospital settings.

We also expanded the service to cover blood antibody testing so eligible users could order at-home antibody tests to check whether they had previously had COVID-19.

But perhaps most significant was introducing the ability to home order rapid lateral flow tests, meaning people could test themselves in their homes and get their result within 30 minutes, without the need for laboratory processing.

Following the initial go-live, we quickly prioritised the need for the home testing service to operate 24/7, with zero downtime during deployments. To accommodate this approach, we created new architecture for the service that was more modular in nature, meaning we broke down tightly coupled code into smaller chunks that could be changed independently.

We adopted the common blue/green deployment pattern which meant we had 2 separate production environments: 1 active and 1 inactive. The status of each environment would change during a release. The new version of the service was first deployed to the inactive environment and then, once the deployment was successfully complete and validated, user traffic was gradually transferred to this environment, so it became active.

Since moving to this pattern, over 110 deployments have been successfully performed with zero downtime.

We also invested in scaling the service to meet the highest anticipated demand. This was achieved through in-depth performance testing and improved optimisation.

Creating a robust and reliable service meant we comfortably dealt with the peak demands throughout the second half of 2021, where we consistently processed over 200,000 orders per day. On the busiest days, we were close to 1 million.

As well as focusing on the delivery of home tests, we also worked closely with Royal Mail to enhance the returns process for PCR tests, which were sent to a laboratory for processing. We incrementally added new functionality to improve and strengthen the service, including home, priority postbox and Sunday collections.

We developed the capability to send hundreds and thousands of tests at once, via our bulk ordering tool, which supported wider surge testing and outbreak control.

In the initial phase, this worked by local authorities providing a list of postcodes specified for testing. The home testing service then retrieved all residential addresses within these postcodes by integrating with the Ordnance Survey 'OS Places API' and sent a test order to all these addresses.

The OS Places API was integrated into the home testing service in the summer of 2020. It enabled users to enter their postcode and select their address from a drop-down list when ordering a home test, removing the need to enter it manually. This API used the latest authoritative addressing data from OS, ensuring greater accuracy in delivering tests.

We expanded our bulk ordering 'push' model into a more sophisticated service, including a custom front end portal that enabled the UK Health Security Agency (UKHSA) Home Testing Operations Team to self-serve in managing bulk orders. This means new use cases can now be rapidly spun up to support targeted testing of large groups.

This functionality has been used in response to many critical events, including supporting the Events Research Programme and sending PCR tests to the COVID-19 antiviral treatments cohort. Across a 10-day period, priority PCR tests were sent to over 1 million vulnerable people in this cohort, meaning they had a PCR test ready and waiting if they started to experience COVID-19 symptoms.

One of the most significant improvements we made within the home testing service was responding to unmatched PCR test results. This occurred when a PCR test was not correctly registered to the person who took the test, meaning their result could not be matched back to them. This registration step was performed by the person taking the test and was frequently cited as a pain point in the user journey.

The team developed a process that automatically linked a person with their test and subsequently with their test result. This pre-registration improvement involved working closely with Royal Mail and their partner Paragon Customer Communications Ltd to link the kit at the point of packing, On processing the order request, Paragon scan the sample barcode on the test package which is used to directly link the test back to the individual.

Within days of introducing this change, the number of unmatched results significantly reduced.

As the pandemic has moved into a new phase, requirements have shifted from enabling high volumes of asymptomatic testing to supporting more rapid response, varied, and nuanced testing use cases.

While some other testing routes have been mothballed but maintained in readiness for any resurgence in the pandemic, other new scenarios have arisen such as tests to support isolation grants. Due to the flexibility of the bulk ordering service, we were able to start processing orders to support isolation grants in less than 2 weeks from receiving the initial request.

The team has been working for some time to transition the home testing service from a rapidly evolving and reactive emergency response, into a flexible, sustainable ongoing capability offering multiple services. This work is now starting to reach fruition.

It is important to recognise that we didn't make all this happen on our own. We have always worked firmly in partnership with our colleagues in the UKHSA Home Testing Operations team. Their management of the supply chain underpinning the service has been critical to its success.

Other key partnerships have been with UKHSA’s fulfilment partners. Firstly, we partnered successfully with Amazon, before then moving to a sustained partnering relationship with Royal Mail and their partner Paragon Customer Communications Ltd. This partnership continues to thrive.

Our delivery partner Kainos has played a vital role in the home testing service. Close collaboration with all other stakeholders across NHS Digital's COVID-19  Test programme and our partners has proved key to the success of the service.

Without all our partners ability to scale rapidly and be lean, quick and secure in data and process, it could not have been possible to deliver the successes that service has enabled, and to have scaled to test the nation as we have done.

The home testing service has moved to an API-based microservices architecture, meaning there are clear boundaries between each component that makes up this service.

Most test orders are now placed through this new architecture which has allowed us to focus on building for future flexibility, faster responses to change and increased self-service for the UKHSA Home Testing Operations team.

In future, new test cohorts or types of orders will be created and managed in real time without requiring code changes or releases, freeing up the development teams to focus on more complex work and acknowledging that in future we will have less dedicated capacity in these teams.