4100 views • Backend System Design
Delivery of notifications is critical for a FinTech company like Razorpay because it is a way to notify customers about their transactions and connect with external systems through Webhooks.
So, how did they design their notification system? let’s find out
Upon every transaction, an event/message was sent to SQS (message broker) which was consumed by a worker that then fanned out the notification through different channels.
Because we want to guarantee delivery, a state was maintained in the database that tells if the notification was successfully sent or not (esp via Webhook).
Hence, there is a component called Scheduler that pulls the unsent notifications from this database and re-queues it in SQS; thus guaranteeing the delivery.
In order to ensure that one type of notification does not affect others, every notification type is classified with some priority and depending on which they are pushed to the corresponding SQS queue.
This ensures that a huge marketing campaign does not affect transactional messages.
To ensure mass notification from one customer does not affect others, we add Rate Limiter that would limit the notifications per customer and per type ensuring that critical notifications always meet the SLA.
We could not scale workers because of high DB load, and hence instead of doing a sync write to the database, the notifications that are unsent and need to be retried are pushed in a sync way to the database.
Because of this async write, we ensure that we write to the database in a staggered way and not put unnecessary load on it.
To ensure we are maintaining our SLA, we have to exhaustively monitor the entire infra for any anomaly; the metrics like - health of the infra, success rate of delivery, and SLA.
If you like what you read subscribe you can always subscribe to my newsletter and get the post delivered straight to your inbox. I write essays on various engineering topics and share it through my weekly newsletter.
924 views • 54 likes • 2022-11-14
When a company scales, they adopt microservices and each service typically gets its own independent database. With data ...
2206 views • 98 likes • 2022-11-07
Authorization plays a critical role in ensuring that the platform is not abused. For example, Instagram ensures that if ...
2572 views • 152 likes • 2022-10-31
Do hyperlocal companies like Uber, Ola, Swiggy, Gojek, Zomato, etc share our phone numbers with the delivery people or t...
2193 views • 81 likes • 2022-10-24
Elasticsearch is a great search engine, but Yelp was not happy with its performance, so they built their own HTTP layer ...
A set of courses designed to make you a better engineer and excel at your career; no-fluff, pure engineering.
Being a passionate engineer, I love to talk about a wide range of topics, but these are my personal favourites.
Arpit's Newsletter read by 21000+ engineers
Weekly essays on real-world system design, distributed systems, or a deep dive into some super-clever algorithm.
Powered by this tech stack.