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**Gerhard Lazu:** So what is better about the new setup? |
**Alan Cooney:** \[11:56\] I can give you the business side, and it will be interesting to hear as well on the technical side. From a business side, it's way more reliable. And you know, you have these problems as a startup, but to give you the example of a host adding their trip - so the guest or customer experience o... |
**Gerhard Lazu:** So the system is a lot more reliable today than it was two years ago. |
**Alan Cooney:** Yes, and that's transposed into other metrics, like many more host sign-ups, and many more trips on the website, just from having this much more robust and easier to use set of tools. |
**Gerhard Lazu:** What about developing the new setup? What is it like writing code for the new setup versus the old setup? |
**Wycliffe Maina:** Yeah, \[unintelligible 00:12:50.02\] It's always easy - or easier - to keep focus, easier to deploy, and easier to know when you have that separation of concerns. You're able to know when you're updating something or not updating something, that is your code is very specific. |
Another thing that \[unintelligible 00:13:14.17\] is tests, which - we have increased the number of tests we have. We have a lot of unit tests, we have always been having \[unintelligible 00:13:24.02\] go for the 100% test coverage... And we are looking to sort of like bring in some integration testing there, and some ... |
But all in all, the scope of this task we are doing actually is, for instance, over the last few months, we have been implementing a few services, and because you're working on a very specific area and it's a Lambda function, it's a little bit easier to work through it, be able to test it, and \[unintelligible 00:13:50... |
**Gerhard Lazu:** That makes a lot of sense... Rather than changing a part of this big whole, now I have discrete units that you can focus your blast area, so to speak, so if there's a failure or a problem, it's limited to that specific service. |
**Wycliffe Maina:** Yeah. |
**Gerhard Lazu:** So did this change the deploy times, basically how quickly the code goes into production? |
**Wycliffe Maina:** Yeah, this is actually the effect of that. The deploy times are like mostly three minutes. The tests are also-- |
**Gerhard Lazu:** Three minutes? |
**Wycliffe Maina:** Yeah. |
**Gerhard Lazu:** Wow... |
**Wycliffe Maina:** Tests are also faster... And it's always easier to get feedback when you are doing deployment. You can even say like -- I would even have like a local \[unintelligible 00:14:29.15\] I would just push it to the CD and see \[unintelligible 00:14:33.03\] That's the one I'm using today, because having d... |
**Gerhard Lazu:** How long did it use to take? |
**Wycliffe Maina:** About 20 minutes? I'm not sure... |
**Gerhard Lazu:** 20 minutes? Wow. And you think that's too long? Some people would say two hours is too long... So it's really interesting that you think 20 minutes is too long, which again, for some would be perfectly okay. So 20 minutes was too long, and now three minutes is just about right, would you say... Right? |
**Wycliffe Maina:** I personally would like it to be a little faster... \[laughs\] |
**Gerhard Lazu:** Wow. Okay... |
**Wycliffe Maina:** Yeah. The faster I can see results of what I'm working on the better. |
**Gerhard Lazu:** Speed is addictive, right? And first of all, as you mentioned, very important - the quicker you can understand your mistake in production, the quicker you can fix it... And if you can do it so quickly that people don't even notice it, isn't that the best? |
**Wycliffe Maina:** Yeah, that's even better. |
**Gerhard Lazu:** Amazing. So back to you, Saul - from an architecture perspective, how many services do you have? Do they interact amongst themselves, do they share anything? What does that look like? |
**Saul Cullen:** That's a really good question. Gosh, I don't know what they were at the last count. We seem to add about one a week as we move over... And as Wycliffe says, we've been doing a lot of this migration. So we keep the services very specific to tasks - we have reviews-related services that handle everything... |
\[16:36\] So these feedback loops is something that -- when you came along, Gerhard, I remember sitting down with you, and you said "We've got to get this DevOps cycle going, and get these feedback loops going really rapidly, so that you can learn from what you put out there and feed that back into what you're working ... |
Another thing we're starting to try as well is including things like feature flags. Instead of pushing out large chunks of code, we'll every day push out multiple new features and just flag them off and show them to specific sets of customers, or ourselves internally, we'll test those. And all of these sort of architec... |
**Break**: \[17:52\] |
**Gerhard Lazu:** I would like to go back, Saul, to how those microservices talk amongst themselves. First of all, my understanding is that those microservices are just collections of serverless functions that get deployed as one unit. So it's just a grouping of serverless functions. They all have their own data store,... |
**Alan Cooney:** I wish there wasn't... \[laughs\] |
**Gerhard Lazu:** Wouldn't it be perfect if there was no network latency, nothing failed? Yeah, sure... |
**Saul Cullen:** Absolutely... I mean, this is something that's an evolving area for us. There's lots of solutions that people tout out there... You know, people using gRPC to communicate between microservices... We're using AWS AppSync, and what we have is we have a separate API service. And that API service allows us... |
\[20:07\] We're still at the early stages of running with this and using it, but at the moment it is working really very well for us, for the most part. Don't know if Alan wants to add anything to that, because it's an area where Alan has really pioneered a lot of that... |
**Alan Cooney:** Yeah, so that's for synchronous communications specifically, which is actually quite a small part of total communication between services... And it's quite an unusual setup actually, in that the services are going back through AppSync -- because often you have a mutation to create a booking, and then t... |
For example, the booking service, when you make a booking, that will put some events onto this sort of central event bus, and then the trip service will listen to that and say "There's a new booking. Let's reduce the number of spaces." And all of that happens in a few seconds, but it's asynchronous, so we don't have to... |
**Gerhard Lazu:** Okay. What sorts of messages do the services put on the Event Bridge? |
**Alan Cooney:** A lot... |
**Gerhard Lazu:** But are they JSON, do you have a specific protocol, do you have any versioning? How do they know how to read those events? Do you have any schemas? How does that look like? |
**Alan Cooney:** Sure. It actually uses the same schema as our API, which makes things very simple. So the booking object on our API is the same as the booking object, as the JSON object that's put on the event bus... Alongside a standard name, so we can create booking updates, something like that. |
**Gerhard Lazu:** Okay. So event bus, not even bridge. |
**Alan Cooney:** Event bridge, which is an event bus, sorry. |
**Gerhard Lazu:** I see, okay. That makes sense. So in terms of number of transactions, volume, latency, anything like that - can you give us some numbers? What looks like a good latency? Do you have such a thing? Do you have any SLOs, any SLIs? Anything around how well services interact? |
**Alan Cooney:** Definitely I think we can get better at this, is the short answer... Most queries respond within 10 milliseconds. For a web app perspective, that's very fast... And that hasn't caused us any issues at the moment. |
**Gerhard Lazu:** And that's internal, right? So the services, when they talk amongst themselves, they can expect asynchronous responses to come back within 10 milliseconds...? |
**Alan Cooney:** Yeah. |
**Gerhard Lazu:** Okay. And what about the public world? Do you have CloudFront? What's in front of the API? |
**Alan Cooney:** This is probably one for Wycliffe, but basically Next.js sits on the front of it... But maybe Wycliffe you can explain a bit about that. |
**Wycliffe Maina:** For the frontend we're using Next.js, which is based on React for those who don't know about that... So most of our important pages, that is the trips pages, the homepage with your trips, hosts, and so on, are SSR-ed. So Next.js goes to the API, fetches the data, and then sends in a fully SSR-ed sta... |
So essentially, what this involves is the fetching between Next.js \[unintelligible 00:23:58.02\] The application is hosted on Vercel, which is the parent company of Next.js, or the company that builds Next.js and open sources it. |
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