by 
I. Overview
II. Vision
III. Goals and Opportunities
Immediate Business Goals
Long Term Business Goals
Business Opportunity
Competitors
IV. Use Cases
Customer Journey
Case 1. Customer orders via PoS
Case 2. Customer orders online
Maintenance and Failure Operations
V. Requirements
Prioritized Architecture Characteristics
1. Enable Discovery - Agility
2. Affordable DevSecOps - Viability
3. Easy to Pivot - Flexibility
4. Availability
5. Security
6. Scalability
7. Performance
Design Constraints
VI. High-Level Architecture
Web/Mobile Experience
Offline Strategy for Smart Fridges
VII. Selected Topics of Mid-Level Architecture
Scheduling System
The Missing Data Tier
How we Avoid Firebase Lock-in
Lean on Data
ChefTec Integration
VIII. Milestones
Milestone 1. Marketing and Analytics
Milestone 2. Mobile App Menu
Milestone 3. Mobile App Orders
Milestone 4. Web Orders
Milestone 5. Customer Profiles
Milestone 6. Multi-Location and Scaling Delivery
IX. ADRs
ADR 1. Hosting Platform
ADR 2. Mobile App Platform
ADR 3. Serverless
ADR 4. Online payment Processing System
ADR 5. Web and Mobile Analytics
ADR 6. Routing and scheduling Software
ADR 7. Newsletters and Client Communication
ADR 8. Smart Fridge Access will be Controlled Both on Prem and via CDN
ADR 9. Google Firebase will be used as Presentation Layer
Farmacy Food is a healthy food startup that takes the “let food be thy medicine” quote literally. This document describes high-level architecture of Farmacy Food’s cloud-based IT infrastructure. It provides essential context followed by a list of key requirements, captured during interviews and research on the startup. A high-level architecture that satisfies those requirements is presented. The document concludes with a project breakdown in delivery milestones. This is a living document and is constantly being updated to reflect changes as the architecture evolves.
We are a community casual restaurant that takes the “let food be thy medicine” quote literally. We want to make healthy meals affordable and accessible that support customers’ health and well-being.
- Make food that is delicious, healthy, nutritionally dense
- Scale operations to enable dozens of automated fridges. Handle 1000s of customers.
- Expand to apartment buildings, college campuses, hospitals, and within businesses
- Scale from City of Detroit to other geographies (Michigan, Ohio, Illinois and nationwide)
- Retain profitability and margins
- Branding; Secure, Affordable and Delivers
- Don’t make any health claims and focus on dietary needs instead
- Donate and support health care workers, senior citizens, and so on and so forth. Support partnership non-profit organizations. We shifted to basically just creating free meals for frontline workers, low-income folks, and folks that were in care in Detroit
- Engage customers with health education and marketing
- Loyalty programs and community engagement
- Be able to collect health screening information from hospitals or physicians (HIPAA compliance)
- Donate money toward paying for a group of people, either a named or unnamed group e.g. feed everybody in the neighborhood altruistically.
- Build an ecosystem of preventative health interventions. Offer customers an initial sizable discount and get a referral fee from gyms, yoga studios, massage therapists, life coaches, et cetera
- Support smartwatches and health trackers
- Potentially become a platform for healthy foods. Enable chefs to create recipes within certain parameters.
- Expand to Children’s meals
- Large market: 18 to 65, young professionals, often dealing with specific health challenges such as high blood pressure, diabetes, et cetera
- Immediately profitable: Most customers pay 12 bucks. It costs an average of $4.25 to produce, package and distribute our meals
- Low setup costs: Able to open up a location for an average of $7,000 comparison to the $500,000 to a million dollars for a restaurant
- Currently 400 meals a week. Between 1,500 to 2,000 meals a week by December
- Six to eight locations before the end of 2020
- 1,000 dedicated customers in early 2021. 10% of them subscription customers. The average meal subscription customer buys 10 meals a week (two meals per weekday)
Any food and beverage-based or restaurant-based business is a competitor. Direct competitors in Detroit are places like Chopped, Seven Grains, Freshy, or Sweetgreen on a national basis.
In order to understand the main requirements we created an advertisment. You can watch it here.
It's quite clear that the main two touch points that will make or break Farmacy Food's business is the mobile app/website and the interaction with the Smart Fridge.
We mapped out the entire customer journey from the order till it's ready on their hands.
These interactions happen after successful acquisition of a customer. Customer acquisition is not covered by this document.
The following customer, and delivery interactions might happen either via web or mobile app. SMS interactions might be supported in the future.
- The customer visits the point of sales
- The customer picks a meal from the fridge
- The PoS owner charges customer’s card and prints an invoice
- The PoS informs the scheduling system for the reduction of stock
- The scheduling system triggers a replenish order if the stock is low
- The PoS informs the accounting system on the sale
- The customer must set-up an account (Including social sign-in Facebook, Gmail, etc.)
- The customer must be logged in
- The customer must set dietary preferences and set health goals
- The customer must be shown available delivery options near an area of their choice (e.g. home or work). The delivery options are home delivery (small delivery fee) and collection from a smart fridge (free). Both are subject to availability in supported locations
- The customer must choose a delivery method
- The customer must be shown time-options for delivery or pick-up. This could be either ASAP where a time must be provided subject to centralized kitchen and delivery‘s availability, or scheduled, where the customer can be offered more flexibility for a later time
- The customer searches for available meals compatible with his preferences and available on the given timeframe
- The customer adds meals to his basket
- The customer must have sufficient credit, or a coupon
- The customer must be able to purchase their credit if necessary
- The customer must be able to confirm discount eligibility during the purchase
- The customer must be presented and order summary and confirm the order
- A confirmation SMS is sent to the customer
- An invoice is sent by email to the customer, via the accounting system
- The order is scheduled by the scheduling system
- The scheduling system informs the stock controller system for the order and the timeframe
- The stock controller system will issue purchase orders if the stock of any ingredients is low
- The stock controller informs the accounting system of the purchase to update the P&L
- The scheduling system informs the delivery system for the order and the timeframe
- The dish or its ingredients aren’t relevant at this stage. Metadata about the order (e.g. cold or warm dish) is sent to the delivery system
- The delivery system schedules delivery and returns a tracking identifier and a container identifier
- At the appropriate time, the order is presented to the centralized kitchen
- The meal is prepared using the ingredients by the centralized kitchen
- The meal is marked as ready on the centralized kitchen dashboard
- The meal is placed on the appropriate container by the centralized kitchen
- The delivery picks the container and travels to the specified location
- In case it’s home delivery
- The delivery gives the customer the order and marks the order as complete by scanning the QR code
- The customer receives a confirmation SMS
- In case of smart fridge delivery
- The delivery replenishes the smart fridge placing orders on the designated cells
- The delivery marks the order as complete by scanning the QR code. The customer receives a notification SMS to pick-up their order
- The customer swipes a credit or debit card they’ve registered in the app, on the back-end of the smart fridge
- The smart fridge releases the order
- The customer receives a confirmation SMS.
- After a specified interval (a day) the customer is sent a feedback email
- Engage the customer by pushing marketing and health education messages
- Emergency Stock. The stock controller must ensure there’s always enough safety stock to support the kitchen.
- Clean the smart fridges. Leftover orders must be returned by the smart fridge operator (e.g. coffee shop). The delivery must be notified via a web/mobile form to pick those up
- Accidents e.g. spills on the fridge must be reported by the smart fridge operator via a web/mobile form. Power outages must be monitored and when prolonged, the food/orders should be considered expired.
- The customer might not receive an order. In case of home delivery, this might happen because the delivery was late or unavailable or any other reason. The customer must be able to dispute the order and get a refund. In case of smart fridge delivery this might happen either due to delivery problems (same as before) or because the fridge is jammed, non-operational, there’s a power outage or the operator is unavailable (e.g. store is closed), Aggregate stats must be collected in both cases and reported to the management.
- The customer might complain about the quality of the order such as meal quality, temperature, quality of cooking, delivery etc. The management is required to follow up in those cases with the goal to retain the customer and improve the process.
- The kitchen might run out of stock or lag behind or be unable to deliver on time for any other reasons. Detailed metrics must be collected and communicated to the management in real time. The management can decide to issue a refund or take other actions to mitigate the issue.
- The stock controller might be unable to purchase ingredients on a price that gives acceptable margin. It must notify the management in order to monitor the situation and take actions such as mark meals as unavailable or provide alternative ingredients.
The architecture must support the use cases described above while satisfying the requirements listed in this section.
The customer experience in acquisition channels (mobile, web and even SMS) must be seamless. This requires custom experimentation and optimization. The architecture must provide ways to capture customer behaviour with comprehensive analytics and support A/B testing. It's a plus if it can also provide rich experiences like smart recommendations powered by AI/Machine Learning. Those features must be immediatelly available on pay-as-you go basis, instead of requiring significant upfront investments in development or technology.
The startup must be able to implement the architecture given budget and time constraints. More specifically this is framed as an integration project where solutions from Software as a Service (SaaS) vendors are integrated using minimal software development. The architecture must be able to be built by delivering features that address the most immediate growth pain points of the business. Complex features that require custom software development must be postponed to as late as possible.
The design must be able to grow as the startup grows. It’s expected that Farmacy Food will pivot several times as it grows. Pivoting should be driven by business needs and not be influenced by rigid architecture structures. In particular architectures that require heavy upfront investment in hardware or software or long-term licencing should be avoided if possible. Careful documentation of processes, requirements and architectural decisions, must make a complete rewrite of every software component, a viable option.
This is a business critical system and this reflects on the Service-Level Objectives (SLOs). The system must be available during core business hours and the website has to be continuously available with the exception of small (up to 2 hours) maintenance windows during low traffic times.
The design must be secure to protect the brand. To have both high security and low costs we must limit the attack surface and avoid holding consumer and sensitive data. Data to be considered include credit card numbers, dates of birth, addresses and emails. Health data is sensitive data and should also be carefully considered. Consulting should be used to ensure compliance with regulatory requirements e.g. PCI for credit cards or HIPAA for health data. The SaaS vendors must also be reputable and provide security assurances.
Scalability requirements are moderate. The architecture needs to be able to support 1000s of users. This is a subsequent requirement for all our SaaS vendors. They should provide assurances of scale and explain how they monitor and stress test their infrastructure.
Customer interactions must be timely to provide a smooth customer experience. This means less than a second for most operations. In exceptional cases where more time is indeed a progress indicator and other interactive components must be used to provide a smooth User Experience (UX). All other (non-customer) interactions should be responsive enough to support operations, but it’s acceptable to be less responsive than the user interactions.
- ChefTec is used for Restaurant Inventory Management & Purchasing
- Toast is used as Point of Sales solution
- Intuit QuickBooks is used for accounting
- There’s an existing mobile application
ChefTec doesn’t have any public available information about their API. Given that most of their off-the-shelf solutions cost in the order of serveral thousand dollars, its consultancy services is unlikely to be cheap. This is a significant risk given how important the central kitchen is for Farmacy Food. ChefTec integrates with QuickBooks for invoicing through add-ons for extra cost.
Toast has an API that one can access after accepting their “API Documentation License Agreement”, here.
QuickBooks has an elaborate API and SDKs.
Directly out of the basic listing of the requirements, and by taking the ADRs into account, this high-level diagram can provide all the necessary use cases.
This is a customer-centric architecture. The customer interacts with Farmacy Food through well designed touch-points. Those are the:
- Cross-platform web and mobile apps
- Smart Fridges also on stores
- Point of Sales Devices on stores
- Web Campaigns that educate and engage
The kitchen is already familiar and satisfied with their ChefTec solution. As long as an API integration solution is found, ChefTec can integrate with the rest of the system. Their backup mechanism can be another way to export data. If these don't work, import/export and manual operations will be required. As the startup scales, it’s likely that this will become a friction point that will make Farmacy Food investigate ChefTec alternatives.
Management oversees operations with emphasis on Marketing and Analytics. This is to be expected for a startup in growth mode. On the other hand, back-end operations are automated to a great extent and don’t require management involvement.
QuickBooks takes care of accounting and payroll. It is integrated with ChefTec and the Toast PoS. The online payments must also be integrated with QuickBooks by using the relevant app.
This Architecture uses SaaS vendors for most of the mundane aspects of the system. This allows the development team to focus on developing the differentiating factors of Farmacy Food. Those are:
The web/mobile experience is the most important differentiating factor of the brand. This allows the customers to order online according to their dietary and health requirements.
By using React Native and Firebase, we avoid spending development time on mundane tasks like login and cross-platform mobile development. The development team can focus on the development of value-adding online functionality and seamless UX.
On the back-end the serverless choice of Cloud Functions means that the team won’t have to worry about building, securing and maintaining servers [1, 2].
The nam5 Multi-Regional location will be used to allow redundancy of critical data and high availability. Replication is handled by Firebase. For the storage and data synchronization needs of the application the Realtime Database will be used based on the best practices for Farmacy Food's needs.
The second key touch point with Farmacy Food customers is the Smart Fridge.
We want to create a decentralized architecture that is robust. It can deliver the products in the smart fridge even with no internet connectivity.
The Smart Fridge is controlled in two ways. The first one is via the toast POS. This has already been proven reliable and it works. The second one is via our oneline order management system.
In order to make this second part decentralized and highly available, we will deliver all orders a fridge is expected to fulfil for a given day in files, that are backed by a CDN. By using a CDN, a very low cost solution, we know that there will be availability at the edge, even if our main systems aren't available or are under maintainance. The files will be fetched periodically by the Smart Fridges and the most current version of the file will be used to allow the firdge to unlock a specific meal.
The lock of the Smart fridge, releases the meal, when the customer presents their credit card. This means that the file must contain a number of hashes of subsets of digits of the credit card's number. The filename can be used as a nonce to partially mitigate dictionary attacks. Date and CVV's will not be in the file. Note also that the above hashing scheme maps the set of hashes to many different cards. This way, even with brute-force attacks, the credit numbers won't be revealed. Worst case, someone might steal a meal, but the computer power required to break the hashing scheme will likely be more expensive than buying the meal in the first place. The container of the meal to be released will also be contained in the file.
The firdge will keep track of which meals have been released. This information must be retained locally and be robust to power loss. Even if the fridge manages to connect only once a day, it is able to fetch the orders for the next day and update the central infrastructure on its status, including the meals it released.
The Scheduling System is a central point where we collect all the (potentially complex) business logic for dispatching and scheduling orders. As described in the use cases, there are complex questions like meal availability that require input from the scheduling system. The options available to a customer for a given time-window can be limited by the availability of delivery or the kitchen and ingredients. The complex logic that is able to answer those questions is included in the Scheduling System. The same system manages order-dispatch from the Web/Mobile UIs to ChefTec and Otter for delivery. This system is responsible with using the APIs of the SaaS platforms to gather information and coordinate their operation.
The main reported drawback of Google Firebase is vendor Lock-In. More specifically it's reported that there are limitted ways to export data and few options that allow you to export data. This has been partially addressed but it's better to be prepared. More specifically we use Firebase as presentation layer. Its databases are used as a form of caching, but the master dataset lives outside firebase, in a managed PostgreSQL. To enable an extra level of decoupling, we use an Event Bus implemented using Cloud Pub/Sub. Modifications to the dataset are also replicated in the Event Bus and Firebase uses those events to update its internal databases and keep in sync. It also uses those updates to push notifications on the Web/App.
This architecture adds some complexity and a few milliseconds of latency on the time it takes for data modifications to reach the App. This is acceptable since those are infrequent compared to other operations e.g. menu search queries.
The major benefit is that our business logic is fully encapsulated behind a REST API and the Event Bus. If we decide to migrate to another presentation layer architecture e.g. create apps that don't use Firebase we can migrate seamlessly without downtime. We can even develop incrementally and operate both fornt-ends in parallel till we have confidence in the transition.
Since we still use Firebase databases, all the intelligence of the platform is available to us. This includes social login, notiffications infrastructure etc. The only key difference is that instead of writing dirrectly to Firebase's database, we do it through our API.
In the Farmacy Food Architecture, there's state stored in various places on the SaaS platforms like Toast and ChefTec. To the extend possible, we don't replicate those data. For example ChefTec has vendor management and personel data. Unless we explicitly need those data, we don't replicate them in our Database. To the extend possible, if there's light use of some of those data, APIs will be used to retrieve the data we need in a timely manner. In cases where APIs are proved to be missing and/or are be slow, those are the only cases where explicit data duplication will be required.
Key takeaways:
- We have a lean data tier. This yields development cost savings as we employ APIs of SaaS services.
- At a certain level caching or data duplication will be required.
- If caching doesn't meet our performance requirements, e can collaborate with SaaS vendors who will be motivated to help given that farmacy food is a significant revenue stream for them. If SaaS vendors aren’t responsive and prevent those errors from getting fixed, alternatives must be explored or the functionality might be re-implemented in house.
We can't find a clear API on ChefTec's website. Of course we can consider the Centralized Kitchen as an independent agent that has to be interfaced manually, but that would be a risk. It might introduce errors like lost orders, and degrade customer experience. It might also prove to be an operational bottleneck preventing the business from scaling to multiple kitchen locations.
To mitigate those risks, we called ChefTec in the number they have for Consultancy Services. We wanted to better understand what it takes to integrate with that system. They were very helpful. We explained to the front desk that we have a potential customer who is asking us to integrate ChefTec with a mobile App we're about to develop. They connected us to Patrick who was very helpful.
He asked for the account, and advised that next time, it will be easier to get more specific answers if we have the customer call, or be on the call. The account name is important. We searched for Farmacy Food in Detroit but it was hard to find.
We explained a little bit better that what we want is the app to be able to schedule orders for the day after. He called that "Schedule a Task" and they have done it many times. He explained that they have done many integrations in the past. One example is QuickBook, so that customers don't have to do double-entries for every order. If it's one they've done before, we might be able to have an dintegration very quickly and with relatively low cost (~$500). This is in line with all the data we see for integrations on the website. If it's a completely custom integration, it can be $5k+. It might also take 60+ days. It needs integration from both the App's side and ChefTec's side. He mentioned that everyone in the "inventory game" (industry), for some unknown reason, doesn't provide APIs.
Bottom line, great call, great communication and clear next steps. We're confident we will be able to integrate and scale with a reasonable budget. It's also clear that they serve thousands of customers and they are very experienced.
- The existing Web and Mobile apps will be enhanced with Google Analytics
- The Web and Mobile apps will be collecting emails of leads and customers
- Any existing e-mails will be migrated to MailChimp
- Education on healthy eating newsletters will engage the customers. Their performance will be evaluated with Analytics
- Glue logic Cloud Function will be developed that keeps MailChimp user database in-sync with the Web App.
- The existing Mobile app will be enhanced to show the menu with information of availability based on the kitchen and the location.
- Customers are able to login (Firebase takes care of social login) and build basic profiles
- Customers can add credit by using the Stripe integration
- Customers can place orders of meals via their mobile app
- Orders are scheduled using ChefTec
- Smart fridges are forwarded sufficient information to release meals in a secure manner (hashes of credit card numbers)
- The website is enhanced to be on-parity with the mobile app
- The customers can build rich profiles through the web and mobile apps
- The available and recommended meals will be customized based on their profiles
- The customers can track records based on meals e.g. calories avoided compared to traditional dining
- The web and mobile apps are enhanced to support multiple cities
- Otter delivery is integrated to enable enhanced delivery scheduling from the centralized kitchen
- Multiple local kitchens on a trial-basis are supported
Status: proposed Context: The architecture needs to be hosted either on dedicated servers or in the cloud. The choice of cloud provider affects the cost of the solution and the time of the implementation. Decision: The platform of choice is the Google Cloud Platform (GCP) on the basis of ease of development, security, versatility and price. To avoid vendor lock-in, no components that don’t have an AWS-equivalent should be used without explicit permission. Consequences: The implementation is expected to scale elastically on demand. We can run experiments and develop staging and test environments easily. AWS remains a migration option if factors like host dictate it at some point. Notably, Google App Engine and BigQuery can not be used because of vendor lock-in concerns.
- Status: Proposed
- Context: The existing mobile application will need to be revamped to enable further use cases.
- Decision: Google Firebase will be used to support. It’s a more mature framework compared to the alternative AWS Amplify. React Native will be used for cross-platform app development. This enables us to have one app instead of one for each platform. React Native is a mature technology developed by Facebook.
- Consequences: The contractors that will be developing the app should be experts on those technologies. Given that they’re the two most widely supported, through competitive bidding, this is expected to reduce development and maintenance costs.
- Status: proposed
- Context: Since traffic isn’t an issue, we can reduce hosting costs by running software in Virtual Machines in GCP (Compute Engine). This means that we will be responsible for building machines and operating them. We can install explicitly RabbitMQ/Kafka, Databases like PostgreSQL and business logic as well as front-end servers (nginx, custom code). On the other hand we could use serverless technologies.
- Decision: Building virtual machines and self-hosting means that the developers will have to spend time maintaining and operating machines. That cost is significant and will slow down development time, since soon a fraction of developer’s time will need to be spent in KTLO. This isn’t a good investment of developers’ time on a startup. As such, Serverless technologies will be used, which are more expensive in terms of hosting, but are managed entirely by Google. Security is also then Google’s responsibility which reduces the attack surface we’re responsible for, under the shared responsibility model.
- Consequences: As part of ADR 1, we decided that only technologies that also exist in AWS will be used. Google Functions will be used for business logic and the equivalent is AWS lambda. Both Python and JavaScript can be used for implementation in both platforms. Care must be taken to avoid using low-level PaaS APIs that would bind the implementation to the platform too much. Appropriate interfaces, owned by us, must abstract PaaS artifacts. Cloud Pub/Sub will be used for queues and the equivalent is AWS SQS. For databases Cloud SQL for PostgreSQL will be used and the equivalent is Amazon RDS for PostgreSQL. Application load balancers and other low-level network artifacts can also be used because they exist in both platforms.
- Status: Proposed
- Context: Beyond the PoS, we now need to process payments online (both in web and mobile) but we don’t want the hassle and regulatory requirements of management of sensitive customer data like credit card numbers. Our branding efforts require use to be a secure platform. We can’t afford information breaches or fraud.
- Decision: Stripe is a suite of payment APIs that enables businesses to manage revenue, prevent fraud, and expand internationally. Beyond the web, it can be integrated with Google’s Firebase mobile framework to receive payments from both iOS and Android devices. It has a rating of 931/950 from UpGuard while PayPal has 912/950. Only phishing attacks have been reported for Stripe while PayPal has data breaches.
- Consequences: The Stripe API is a REST API and it’s straightforward. There’s the need to redirect the customer to Stripe Checkout. The keys should be kept safe. SSL certificates should be checked while making API calls and only whitelisted IPs should be trusted. Integration security guide must be followed. All communication should be verified with Stripe’s PGP key.
- Status: Proposed
- Context: In order to grow the customer base and measure the effectiveness of marketing spending, we need to capture key metrics about our customer’s journey through our web and mobile assets.
- Decision: Google Analytics is the de facto platform for online analytics that supports both web, mobile and connected devices analytics. Since we don’t treat this analytics information as sensitive or intellectual property data, we can trust Google for the collection, analysis and presentation. They are free, well integrated with their advertising platform and marketing agencies know how to use it. Several alternatives we examined, including Kissmetrics, Heap and GoSquared, often lack significant features, have more difficult or missing API integrations for mobile and they aren’t free.
- Consequences: We have to integrate Google Analytics with our React Native App early, to allow us to build baselines for our traffic and track errors during the development process.
- Status: Proposed
- Context: In order to scale delivery both at home and on the smart fridges, we need a delivery optimization and scheduling system.
- Decision: Otter will be used as a starting point for delivery optimization, on the basis of very quick integration, since it already supports Toast as part of its integrations. It also supports Uber Eats, Caviar and Postmates for ordering. Alternatives like OptimoRoute or Circuit can be employed when scale proves to be a problem.
- Consequences: The direct integration means that we have limited access and flexibility.
- Status: Proposed
- Context: We need to engage customers with health education. This must be driven by business and must be mails with rich content including images.
- Decision: MailChimp is chosen as a customer communication platform on the basis of credibility, pricing and ease of use from non-technical users. For rich SMS interactions, Twilio will, where necessary, be used on the basis of credibility, reliability and affordability.
- Consequences: The lists of Mailchimp must be synchronized with the rest of the system.
- Status: Proposed
- Context: The smart fridge must be available. We can't afford to have a customer who has the right to a meal be denied access to it, because of network or software unavailability.
- Decision: We use a file-based solution. We use Google's CDN for file distribution. The fiile will adhere to all the secruity requirements and still will allow the Smart Fridge to operate reliable while offline for prolongued periods of time.
- Consequences: A security audit of the protocol will have to be performed.
- Status: Proposed
- Context: We want to be able to switch in a different front-end system easily. The switch might be movitvated by any reasons including financial or growth that is prevented by missing features. We shouldn't have to re-implement everything from scratch because the implementation is too tied-up to Google Firebase. This typically reflects on where data is stored and the way Apps use to access those data.
- Decision: We hold the master dataset outside Google Firebase, in the managed PostgreSQL. Firebease modifies it by using a REST API that abstract the core business logic. Dataset modifications are replicated to Firebase's datastore by using an Event Bus (Event Queue).
- Consequences: Firebase and core business logic are completely decoupled. The implementation is more complex, but only where it matters. We can operate more than one front-end system e.g. to during a migration period. This abstraction also allows us to deliver push notification to customers by proxying a part of the Event Bus stream. Since we do use Firebase's datastore (although not as a master dataset), we have access to all the productivity features it provides.
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