A short history of web frameworks What is a web framework? A web framework is a set of tools for the rapid development of server-side applications that provides a boilerplate to simplify the implementation of common tasks. According to MDN, those tasks are routing URLs to appropriate handlers, interacting with databases, supporting sessions and user authorization, formatting output (e.g. HTML, JSON, XML), and improving security against web attacks. The most popular web frameworks are Ruby on Rails, Django, Flask, FastAPI, Express, Laravel.

Highlights Pinterest: Shallow Mirror Kafka MirrorMaker is a tool to replicate Kafka clusters across different regions. Data from different Source Brokers is transferred to MirrorMaker which then sends this data to Destination Brokers in other regions. Pinterest started experiencing scalability issues at some point. Monitoring showed some CPU and memory spikes. During the investigation, it became apparent that most of the CPU time was spent on message decompression and recompression. Memory consumption was often 2-10 times bigger than the actual data being sent.

Highlights AWS: Diving Deep on S3 Consistency Werner Vogels, CTO at Amazon, shares the journey of building strong consistency for AWS S3. When S3 was launched 15 years ago in 2006, it was simple storage for files, backups, etc. The eventual consistency model was more than enough for such purposes. This means that sometimes API would return an older version of the object that was not yet propagated through the nodes.

Highlights Instacart: Don’t let the crows guide your routes Instacart connects shoppers to make purchases and deliver them to the app customers. To make it more efficient, the application should calculate optimal routes to make purchases and deliver orders. The easiest and the most naïve solution to calculate the path between two dots on a map is to calculate Haversine Distance - a straight line between two dots, similar to a bird flying between them.

Highlights DoorDash: Optimizing OpenTelemetry’s Span Processor for High Throughput and Low CPU Costs With an effort to migrate from the monolith to microservices, there is a need to trace requests between these services. OpenTelemetry is a new project aiming to become a standard. As a request hits a system, OpenTelemetry assigns a unique ID, all the underlying services (called spans) receive the same ID. Spans data is being collected on a local collector, then it’s sent to a collector gateway.

Highlights FullContact: Improving the Graph: Transition to ScyllaDB FullContact set an ambitious goal of 10,000 QPS. Initially, they moved their database from HBase to Cassandra. Cluster consisted of 3 instances of c5.2xlarge EC2 + 2 TB of gp2 EBS storage. With the growing amount of records in the database, response time crept from 100 ms to 300 ms. It turned out that the default Size Tiered Compaction Strategy is optimized for inserts which lead to a single file for SSTable.

Highlights GitHub: How we scaled the API with a sharded, replicated rate limiter in Redis GitHub API has a limit on API calls per key. Such keys were stored in Memcached along with their reset_at value and number of calls. Memcached was also used for application caching purposes. Such a solution works well but harder to scale. It was decided to have one Memcached per datacenter, in which case clients can face some issues if requests hit different datacenters.

Highlights Kiwi.com: Nonstop Operations with Scylla Even Through the OVHcloud Fire Fire on French OVHcloud affected four datacenters: SBG2 was destroyed, SBG1 adjacent rooms were partially on fire, SBG3 and SBG4 were switched off to fight the fire. Overall, 3.6 million websites were affected, including banks and mail servers. Kiwi.com uses Scylla - NoSQL database, as a highly available and resilient solution. Their monitoring system detected spikes as nodes went down but later other OVHcloud datacenters took over the requests.

Highlights Aurora: Payment Acquiring Solution with CockroachDB on Kubernetes Aurora is the company that handles credit card payments. Such transactions should work all the time, be consistent and scalable. That’s why they migrate from PostgreSQL to CockroachDB: eventual consistency is not an option in this business. CockroachDB guarantees serializable transactions. This blog post describes higher level architecture of the solution. Tech stack: .NET Core C#, ReactJS, CockroachDB. Key takeaways. Hybryd-Cloud: Google Cloud + 2 co-location, never be 100% cloud or 100% private, hence no vendor lock, better availability if certain cloud provider goes down.

Highlights Slack: Migrating Millions of Concurrent Websockets to Envoy Slack makes an extensive use of websocket technology for their messaging service. Historically, they used HAProxy as a load balance, however, they faced an issue with dynamic updates of a list of endpoints. They could also change config and restart a load balancer which is tricky as it has to maintain existing websocket connections. They’ve decided to switch to Envoy proxy as it allows dynamic change of the configuration.