Notification and Reminder Systems

Just build notifications - sounds simple, right? Until you realize you’re not just sending messages -  you’re building a real-time distributed delivery system that must work even when the app is off. Challenge 1: When the app is ON (foreground) If your app is open, you can’t rely on push notifications alone. You need real-time, in-app updates - instant, without reloads. ✅ Solution: Use WebSockets (or Server-Sent Events) for live updates. Maintain a notifications channel per user - e.g., ws://https://lnkd.in/gx3PHizf. On the server, publish events to Redis Pub/Sub or Kafka when new notifications are created. Your WebSocket service listens and pushes them instantly to connected clients. The frontend listens to the stream and updates the local store 🧠 Tip: Always acknowledge messages from the client to mark them as “delivered.” If the WebSocket disconnects, keep track of the last delivered notification ID so the next connection can fetch missed ones via REST fallback. Challenge 2: When the app is OFF (background or closed) This is where most systems break. If you only use WebSockets, users never see anything when the app is off. ✅ Solution: Use Push Notification Gateways (Firebase Cloud Messaging for Android/Web, APNs for iOS). When a new notification is generated, check user’s online status (via presence tracking). If user is offline -> send via push provider (FCM/APNs). If user is online -> send via WebSocket only. Store every notification in your notifications table for later sync. 🧠 Tip: FCM can also send data-only payloads - so when the app wakes up, it syncs new notifications silently before showing them. For iOS, remember: background refresh is limited - so keep payloads minimal. Challenge 3: Synchronizing between real-time and stored notifications You might send via WebSocket instantly, but what if the user refreshes the page? You need to persist notifications, not just stream them. ✅ Solution: Every notification is first written to a database (or event store) before being delivered. Frontend loads all unseen notifications from /api/notifications?status=unread on mount. Then subscribes to the WebSocket for future ones. This ensures no message is ever lost between app reloads. 🧠 Tech stack pattern: Postgres + Kafka + Redis + WebSocket gateway Web app fetches persisted data -> subscribes for live events Challenge 4: Delivery status and retries Push tokens expire. WebSockets disconnect. You must know whether the user actually received the message. ✅ Solution: Track three states: SENT, DELIVERED, READ. For WebSocket: Server emits notification Client acknowledges (ACK) with notification ID → mark as DELIVERED For Push: Listen to provider responses (e.g., FCM returns InvalidRegistration or NotRegistered) Remove bad tokens and retry with fallback channel (like email). 💭 The takeaway “Just send a notification” sounds simple. But making it reliable is one of the hardest distributed engineering problems you’ll face.

Some texts are too important to forget, so I made sure they send themselves. That’s exactly the little prototype I worked on today. The story: My sister is a hostelite, and almost every day she forgets to notify my mother when she reaches her University. Naturally, my mother being at home gets worried until she hears from her. So, I thought: why not automate this tiny, yet meaningful task? How it works: • You set a place once (give it a name + longitude & latitude). • Add a custom or default message (in my case: “Hi Mama, I’ve reached the University”). • The reminder stays saved until you delete it. • The system keeps checking your live location in the background. • The moment you’re within ~200 meters of the saved place, the distance is calculated, the message is prepared, and within seconds… your loved one gets the text. Under the hood (tech side): • Geocoder for fetching live latitude & longitude. • Haversine formula to calculate distance between two geo-points. • pywhatkit for automating WhatsApp messages. • JSON storage to persist reminders even after restarts. • A background thread that checks every minute, ensuring messages send only once per day per reminder (no spam). No typing. No distractions. No missed notifications. Just peace of mind for both sides. And while this is a small prototype, imagine the possibilities: ✅ Automatic attendance marking ✅ Location-based alerts ✅ Real-time family updates ✅ Safety notifications Sometimes, solving even the tiniest pain points is where technology feels most powerful. #TechForGood #python

Everyone talks about what you should do before you push to production, but software engineers, what about after? The job doesn’t end once you’ve deployed; you must monitor, log, and alert. ♠ 1. Logging Logging captures and records events, activities, and data generated by your system, applications, or services. This includes everything from user interactions to system errors. ◄Why do you need it? To capture crucial data that provides insight into system health user behavior and aids in debugging. ◄Best practices • Structured Logging: Use a consistent format for your logs to make it easier to parse and analyze. • Log Levels: Utilize different log levels (info, warning, error, etc.) to differentiate the importance and urgency of logged events. • Sensitive Data: Avoid logging sensitive information like passwords or personal data to maintain security and privacy. • Retention Policy: Implement a log retention policy to manage the storage of logs, ensuring old logs are archived or deleted as needed. ♠ 2.Monitoring It’s observing and analyzing system performance, behavior, and health using the data collected from logs. It involves tracking key metrics and generating insights from real-time and historical data. ◄Why do you need it? To detect real-time issues, monitor trends, and ensure your system runs smoothly. ◄Best practices: • Dashboard Visualization: Use monitoring tools that offer dashboards to present data in a clear, human-readable format, making it easier to spot trends and issues. • Key Metrics: Monitor critical metrics like response times, error rates, CPU/memory usage, and request throughput to ensure overall system health. • Automated Analysis: Implement automated systems to analyze logs and metrics, alerting you to potential issues without constant manual checks. 3. Alerting It’s all about notifying relevant stakeholders when certain conditions or thresholds are met within the monitored system. This ensures that critical issues are addressed as soon as they arise. ◄Why do you need it? To promptly address critical issues like high latency or system failures, preventing downtime. ◄Best practices: •Thresholds: Set clear thresholds for alerts based on what’s acceptable for your system’s performance. For instance, set an alert if latency exceeds 500ms or if error rates rise above 2%. • Alert Fatigue: To prevent desensitization, avoid setting too many alerts. Focus on the most critical metrics to ensure that alerts are meaningful and actionable. • Escalation Policies: Define an escalation path for alerts so that if an issue isn’t resolved promptly, it is automatically escalated to higher levels of support. Without these 3, no one would know there’s a problem until the user calls you themselves. 

🚨 Boosting Community Sign-Ups for Electronic Mass Notification 🚨 As emergency managers, one of our key challenges is maximizing community enrollment in electronic mass notification systems. These systems are vital for timely alerts, but their effectiveness hinges on widespread community participation. Here's a strategic approach to increase sign-up rates: 1. Community Workshops and Seminars: Host informative sessions explaining the benefits and workings of the alert software. Use real-life scenarios to demonstrate the system's impact on safety. 2. Collaborate with Local Organizations: Partner with schools, businesses, and community groups to spread the word. Leverage these networks for distributing sign-up information and materials. 3. Utilize Social Media Platforms: Create engaging content that highlights the importance of staying informed during emergencies. Share testimonials and success stories to build trust and credibility. 4. Local Media Engagement: Work with local newspapers, radio stations, and TV channels to reach a broader audience. Regular segments or announcements can keep the community informed and encourage sign-ups. 5. Visible Presence at Community Events: Set up booths at fairs, markets, and public gatherings to facilitate on-the-spot sign-ups. Use these opportunities for live demonstrations and Q&A sessions. 6. Incentivize Sign-Ups: Collaborate with local businesses to offer discounts or incentives for those who sign up. Small rewards can be a significant motivator for participation. 7. Feedback and Improvement: Conduct surveys to understand community hesitations and improve outreach strategies. Address common concerns in your communications to increase trust and participation. 8. Regular Updates and Reminders: Keep the community informed about the system’s updates and success stories. Regular reminders can prompt those not signed up yet to act. By implementing these strategies, we can increase community engagement with electronic mass notification systems, ensuring that more people are informed and prepared in the face of emergencies. Let's share more ideas and strategies. What has worked in your community? #EmergencyManagement #EmergencyManagers #CommunityOutreach #MassNotification #PublicSafety #EmergencyPreparedness

If you’re only thinking about digital CS as a means to engage your customers, you’re missing a critical part of its value. Internal communication and automation is a severely undervalued use case for digital CS. You should be using digital internally in two ways: 1. Trigger alerts or notifications to internal stakeholders based on customer behavior 2. Automate repetitive manual CSM tasks Utilizing digital like this is powerful. It’s so often overlooked, and this is a huge missed opportunity. Not only does it make everybody’s job easier, but by cutting out so much manual work, it also leads to huge increases in efficiency and productivity. Less copy and pasting or searching for information means more time for more important things. Sometimes that looks like the ability to increase the number of accounts assigned to each CSM, other times it simply opens up time in their week to actually be able to have the strategic conversations we all want them to be having. Here are some examples of how to effectively use both: Alerts & notifications - Notify a CSM 6 months before a customer’s renewal date so they’re planning early for how to retain and grow the account - Alert a CSM if a customer has too many open support tickets or if they haven’t logged in for 30 days - Notify a digital CS program manager when customers renew at more than double their prior year spend - include a reminder to ask their CSM if the account is a candidate to provide a testimonial or case study or become a reference - Alert a frontline manager if one of their CSMs has a sudden increase in accounts with “red” customer health, so they can provide any additional support that team member needs Repetitive manual tasks: - Renewal reminders sent to customers automatically at your preferred cadence - Self-service usage dashboards customers can look at whenever, so they don’t have to bug their CSM to find out how many open licenses they can still assign or how much their team is actually using the product - Pre-populated EBR decks, or better yet, entirely automated EBRs - Anything that currently requires your CSMs to copy and paste the same thing over and over There are unlimited possibilities here! How else have you used digital CS to improve operational efficiency internally? #customersuccess #digitalcustomersuccess #digitalcs #internalcommunication

You ever realize you never followed up with someone who said, “Yeah, I’m interested”? Multiply that by 50. That’s your hidden capital. Most raisers hear those words and think they’ve got a commitment. They don’t. They’ve got a window. And it closes fast. Here’s what should happen next. 𝗤𝘂𝗶𝗰𝗸 𝗰𝗼𝗻𝗳𝗶𝗿𝗺𝗮𝘁𝗶𝗼𝗻 → Send a short note right away. “Great to hear, [Name]. I’ll send a few details about what comes next.” Simple. Immediate. Professional. 𝗖𝗹𝗲𝗮𝗿 𝗳𝗼𝗹𝗹𝗼𝘄-𝘂𝗽 𝘄𝗶𝘁𝗵𝗶𝗻 𝟮𝟰 𝗵𝗼𝘂𝗿𝘀 → Share what you invest in. How your process works. What step comes next. No pitch. Just clarity. Workflow Step #1. 𝗔 𝗴𝗲𝗻𝘁𝗹𝗲 𝗿𝗲𝗺𝗶𝗻𝗱𝗲𝗿 → If they don’t act, your system checks in three days later. “Want to hop on a quick call to talk through what we’re working on?” You’re not chasing. You’re staying visible. 𝗔𝘂𝘁𝗼𝗺𝗮𝘁𝗲𝗱 𝗲𝗱𝘂𝗰𝗮𝘁𝗶𝗼𝗻 → Still nothing? Your CRM sends value-driven follow-ups. A story from a past project. How you structure investor returns. A market update or recent win. You keep showing up. They keep remembering. 𝗣𝗲𝗿𝘀𝗼𝗻𝗮𝗹 𝗰𝘂𝗲 → If someone keeps opening but doesn’t book, your CRM flags it. That’s your cue to reach out. The system tracks interest. You act on it. L𝗼𝗻𝗴-𝘁𝗲𝗿𝗺 𝗻𝘂𝗿𝘁𝘂𝗿𝗲 → If they’re not ready, they move to your update list. They’ll get your quarterly or monthly insights. You stay top of mind. That’s real follow-up. Not memory. Not luck. A system that remembers for you. → “I’m interested” doesn’t close the deal. It starts the workflow. Which stage above are you not following up on right now? Tell me where the gap is → I’ll give you one automation idea to fix it.

Interviewer: Design a notification service My answer: Challenge accepted, let’s go! 1. what even is a notification system? it’s a system that delivers alerts to users through: ‣ in-app (that bell icon) ‣ push notifications (on mobile or web) ‣ email (for things that can wait) the goal? to tell the right person, the right thing, at the right time — without breaking under millions of users. 2. what happens when an event occurs? a user does something — say, UserA likes your post. question: how does the system know to tell you? → the app calls an API like /notify and sends: { "event_type": "like", "actor": "UserA", "receiver": "UserB", "object": "Post123" } this is the trigger. the system now knows something happened and who cares about it. 3. how do we make sure it doesn’t break under load? millions of events can happen at once. if we handle them immediately, we crash. so we ask: can we queue them instead? → yes. we push every event into a queue (Kafka or RabbitMQ). this lets the app move on fast, while workers handle the heavy lifting later. 4. who processes the queue? a worker picks up each event and starts thinking: ‣ what happened? ‣ who should get this? ‣ how do they want to get it? it checks the user’s preferences (in Redis or DB): “does UserB want push alerts or just in-app?” then it builds a nice message like: UserA liked your post “How to scale systems.” 5. how does it reach the user? now comes the fan-out step. the worker sends this message through the right channels: ‣ In-App → save it in DB (so it shows under the bell icon) ‣ Push → send via FCM/APNs ‣ Email → queue in SES/SendGrid question: what if something fails? 6. what if sending fails? every channel has its own service with retry logic. if a push fails, it tries again (3–5 times, with a delay). we also log everything: sent, failed, or skipped. and if a message just keeps failing? we move it to a Dead Letter Queue (DLQ) to analyze later. 7. how does the user see it? the app just calls: /notifications?user=UserB and fetches from the database. → you see “UserA liked your post” with a “read/unread” flag. simple, fast, familiar. 8. how do we scale this? big systems need smart tricks: ‣ Kafka/RabbitMQ → to handle massive event traffic ‣ Redis cache → for fast preference lookups ‣ Hashing → to avoid duplicate notifications ‣ Batching → to group low-priority ones (“Your 10 posts got likes today”) 9. how do we make it reliable? idempotent writes → no double sends exponential backoff → retry smartly DLQ → never lose failed messages metrics → track success/failure alerts → if queue grows too long this ensures it delivers billions of messages quietly, on time, and with care. 𝗪𝗼𝗿𝗸𝗶𝗻𝗴 𝗼𝗻 𝗝𝗮𝘃𝗮 𝗶𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄𝘀? I’ve got you covered 𝐂𝐡𝐞𝐜𝐤 𝗼𝘂𝘁 𝘁𝗵𝗶𝘀 𝗱𝗲𝘁𝗮𝗶𝗹𝗲𝗱 𝗝𝗮𝘃𝗮 𝗕𝗮𝗰𝗸𝗲𝗻𝗱 𝗗𝗲𝘃𝗲𝗹𝗼𝗽𝗺𝗲𝗻𝘁 𝗣𝗿𝗲𝗽 𝗞𝗶𝘁: https://lnkd.in/dfhsJKMj 40% OFF for a limited time: use code 𝗝𝗔𝗩𝗔𝟭𝟳 #Java #Backend #JavaDeveloper

How do you design an Event Notification System for a user base of 220 Million active users ? Netflix has more than 220 million active members who perform a variety of actions throughout each session, ranging from renaming a profile to watching a title. Reacting to these actions in near real-time to keep the experience consistent across devices is critical for ensuring an optimal member experience. This is not an easy task, considering the wide variety of supported devices and the sheer volume of actions our members perform. Netflix created a system called "RENO" (Rapid Event Notification System) System Requirements: Providing a seamless and consistent Netflix experience across various platforms (iOS, Android, smart TVs, Roku, Amazon FireStick, web browser) and various device types (mobile phones, tablets, televisions, computers, set top boxes) requires more than the traditional request-response model. Use cases 1. Viewing Activity When a member begins to watch a show, their “Continue Watching” list should be updated across all of their devices to reflect that viewing. 2. Personalized Experience Refresh Netflix Recommendation engine continuously refreshes recommendations for every member. The updated recommendations need to be delivered to the device timely for an optimal member experience. 3. Membership Plan Changes Members often change their plan types, leading to a change in their experience that must be immediately reflected across all of their devices. 4. Member “My List” Updates When members update their “My List” by adding or removing titles, the changes should be reflected across all of their devices. 5. Member Profile Changes When members update their account settings like add/delete/rename profiles or change their preferred maturity level for content, these updates must be reflected across all of their devices. 6. System Diagnostic Signals In special scenarios, we need to send diagnostic signals to the Netflix app on devices to help troubleshoot problems and enable tracing capabilities. Design Decisions : 1. Single Events Source(all events coming to one place) 2. Event Prioritization(Some events are important than the other) 3. Hybrid Communication Model(some devices may be offline when we push notifications so they need to fetch their notifications when they come online) 4. Targeted Delivery(Distribute sending notifications based on devices to different systems like ios, android, smart tv etc.) 5. Managing High RPS(requests per second) More on the official blog here : https://lnkd.in/ghBUnSNS PS: This is an awesome read ! I like the push and pull model being combined here :)

🧠💼 How scheduled tasks are transforming client project management at Mchange.pl   Managing client projects isn’t just about staying organized,it’s about addressing the deeper challenges that drive success. At Mchange.pl, we’re taking project management to the next level with AI-powered tools like ChatGPT’s Scheduled Tasks. Here’s how we’re creating real impact for our clients:   📅 Never miss a milestone. Deadlines matter, but key milestones are where success is built. We use scheduled reminders to track critical tasks, ensuring nothing slips through the cracks. Example: “Remind me 3 days before the delivery date of the Mchange.pl Transformation project to check on progress.”   💬 Listening to clients, always. Client feedback drives improvement. That’s why we schedule follow-ups after each project phase to gather insights and ensure satisfaction. Example:“Remind me to send a feedback request after completing a phase of the Mchange.pl AI Adoption project.”   📊 Strategic alignment, every Step. Client goals evolve, and we make sure our projects keep pace. Quarterly reminders help us assess alignment with their long-term objectives. Example:“Set quarterly reminders to review how our ongoing projects align with Mchange.pl strategic goals.”   📝 Proactive communication. Keeping clients informed is key. We automate reminders for monthly progress updates, so clients always know where their projects stand. Example:“Remind me to send monthly progress reports to Mchange on the ongoing digital transformation project.”   ⭐ Ensuring post-project Satisfaction. Our commitment doesn’t end at delivery. We schedule post-project reviews to evaluate outcomes and gather valuable feedback. Example:“Set a reminder to schedule a post-project review meeting with Mchange two weeks after the project is delivered.”   📚 Ongoing training & support. For clients with training or support needs, we use reminders to follow up consistently, ensuring they’re always equipped to succeed. Example: “Remind me quarterly to check in with Mchange for training updates on their new platform.”   🌟 At Mchange.pl, we believe AI isn’t just about technology, it’s about transforming workflows, solving real pain points, and driving client success. If your projects aren’t reaching their full potential, let’s change that.   ✔️ Talk to your clients to uncover their true frustrations. ✔️ Use AI to tackle deeper challenges. ✔️ Update your workflows to reflect real transformation.    👉Ready to transform your client interactions? Visit us at www.Mchange.pl or reach out today.   #AIIntegration #WorkflowAutomation #DigitalTransformation #ProjectManagementTools #ClientSuccess #AIInnovation #EfficientWorkflows #BusinessEfficiency #TeamTraining #ClientSatisfaction