Consul

As we've evolved or added additional infrastructure to our stack, we've biased towards managed services. Most new backing stores are Amazon RDS instances now. We do use self-managed PostgreSQL with TimescaleDB for time-series data—this is made HA with the use of Patroni and Consul.

We also use managed Amazon ElastiCache instances instead of spinning up Amazon EC2 instances to run Redis workloads, as well as shifting to Amazon Kinesis instead of Kafka.

Since the beginning, Cal Henderson has been the CTO of Slack. Earlier this year, he commented on a Quora question summarizing their current stack.

• Web: a mix of JavaScript/ES6 and React.
• Desktop: And Electron to ship it as a desktop application.
• Android: a mix of Java and Kotlin.
• iOS: written in a mix of Objective C and Swift.

• The core application and the API written in PHP/Hack that runs on HHVM.
• The data is stored in MySQL using Vitess.
• Caching is done using Memcached and MCRouter.
• The search service takes help from SolrCloud, with various Java services.
• The messaging system uses WebSockets with many services in Java and Go.
• Load balancing is done using HAproxy with Consul for configuration.
• Most services talk to each other over gRPC,
• Some Thrift and JSON-over-HTTP
• Voice and video calling service was built in Elixir.

• Built using open source tools including Presto, Spark, Airflow, Hadoop and Kafka.

• For server configuration and management we use Terraform, Chef and Kubernetes.
• We use Prometheus for time series metrics and ELK for logging.

Postmates built a tool called Bazaar that helps onboard new partners and handles several routine tasks, like nightly emails to merchants alerting them about items that are out of stock.

Since they ran Bazaar across multiple instances, the team needed to avoid sending multiple emails to their partners by obtaining lock across multiple hosts. To solve their challenge, they created and open sourced ConsulMutEx, and an Elixir module for acquiring and releasing locks with Consul and other backends.

It works with Consul’s KV store, as well as other backends, including ets, Erlang’s in-memory database.

All our services use Consul for discovery, configuration and cluster management (auto scaling, health monitoring, dynamic reconfiguration, leader elections) Consul