Meaning
An intermediate routing layer replicates all database writes and sends them to both a legacy system and a new system simultaneously. A dual write bridge holds the two databases in parallel alignment while the new infrastructure undergoes active testing. This technique allows for live validation of the replacement environment.
Routing Method
The application server directs transactions to a proxy that bifurcates each write request. Using a dual write bridge, the application receives a success confirmation only after both target repositories acknowledge the write or after a specific async policy is met. This ensures that both databases remain consistent.
System Latency
Network overhead and write times increase when every database transaction is duplicated across different paths. Because the dual write bridge must wait for twice the number of responses, the application layer often experiences higher response times, which can degrade the user experience during peak traffic hours. Managing this latency requires high-speed connections between the data centres.
Failure Scenario
A write failure on one side of the bridge requires a queuing mechanism to store the transaction for later retry. If the retry fails, the bridge enters an out-of-sync state that must be resolved through an offline comparison tool.
