Extract Product Lines

To do effective legacy displacement, we need to figure out how to break down the problem into manageable pieces. Extract Product Lines does this by identifying product lines and using them as the basis for migration. more…

3d

Patterns of Legacy Displacement

My colleagues do a lot of work that involves replacing legacy software systems. Three of my colleagues - Ian Cartwright, Rob Horn, and James Lewis - have started to capture their experience and advice for this is a collection of patterns. We begin with an overview article that lays out four main categories of activity that...

4d

Hybrid Clock

While a Lamport Clock is often necessary to order events in a distributed system, clients often need to know the actual times too. The Hybrid Clock, Unmesh's next pattern, combines these two demands. more…

4d

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Bacharach, Rhineland-Palatinate, Germany (2016)

4w

Follower Reads

When you are using Leaders and Followers, you can use Follower Reads to achieve better throughput and lower latency. However there is always a replication lag between the leader and the followers, so you may need to take action to preserve consistency. more…

4w

Stepping Back from Speaking

A personal note on why I wish to give up doing talks more…

4w

Version Vector

A Lamport Clock is effective to order events on a single server, but with multiple servers we need a vector of version numbers to detect concurrent updates. more…

4w

Hybrid Clock

While a Lamport Clock is often necessary to order events in a distributed system, clients often need to know the actual times too. The Hybrid Clock, Unmesh's next pattern, combines these two demands. more…

5w

Lamport Clock

Next distributed system pattern from Unmesh is the Lamport Clock. Distributed systems can't assume that time is consistent between servers, and sometimes time goes backwards. Yet it's important to have some way to order events. more…

Jun 2021

Versioned Value

When a distributed system has mutable data, nodes need to know which is the most recent value, so a versioned value stores a version number with every value. more…

Jun 2021