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Microservicessystem_design~10 mins

Strangler fig pattern in Microservices - Interactive Code Practice

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Practice - 5 Tasks
Answer the questions below
1fill in blank
easy

Complete the code to describe the main goal of the Strangler fig pattern.

Microservices
The Strangler fig pattern helps to [1] an old system gradually by building a new system around it.
Drag options to blanks, or click blank then click option'
Aarchive
Bignore
Cduplicate
Dreplace
Attempts:
3 left
💡 Hint
Common Mistakes
Thinking the pattern duplicates the old system instead of replacing it.
Assuming the old system is ignored during migration.
2fill in blank
medium

Complete the code to identify the first step in applying the Strangler fig pattern.

Microservices
The first step is to [1] some requests to the new system while the old system still runs.
Drag options to blanks, or click blank then click option'
Aroute
Bshut down
Cignore
Dbackup
Attempts:
3 left
💡 Hint
Common Mistakes
Thinking the old system is shut down immediately.
Assuming the new system ignores requests at first.
3fill in blank
hard

Fix the error in the description of the Strangler fig pattern.

Microservices
The Strangler fig pattern involves [1] the entire old system at once and then building a new one.
Drag options to blanks, or click blank then click option'
Ashutting down
Bignoring
Creplacing
Dduplicating
Attempts:
3 left
💡 Hint
Common Mistakes
Believing the old system is shut down immediately.
Confusing ignoring with gradual replacement.
4fill in blank
hard

Fill both blanks to complete the code snippet describing request handling in the Strangler fig pattern.

Microservices
Requests are [1] to either the old system or the new system based on [2] rules.
Drag options to blanks, or click blank then click option'
Arouted
Bignored
Crouting
Dbackup
Attempts:
3 left
💡 Hint
Common Mistakes
Using 'ignored' instead of 'routed' for requests.
Confusing 'backup' with 'routing' rules.
5fill in blank
hard

Fill all three blanks to complete the code describing the migration process in the Strangler fig pattern.

Microservices
The migration involves [1] features from the old system, [2] them in the new system, and [3] traffic gradually.
Drag options to blanks, or click blank then click option'
Aextracting
Btesting
Cshifting
Dignoring
Attempts:
3 left
💡 Hint
Common Mistakes
Ignoring testing before shifting traffic.
Trying to shift traffic without extracting features first.

Practice

(1/5)
1. What is the main goal of the Strangler fig pattern in microservices architecture?
easy
A. To build all new services from scratch before replacing the old system
B. To merge all services into a single monolithic application
C. To run the old and new systems completely separately without integration
D. To gradually replace parts of a legacy system with new services

Solution

  1. Step 1: Understand the pattern's purpose

    The Strangler fig pattern is designed to replace legacy systems gradually, not all at once.

  2. Step 2: Compare options with the pattern goal

    To gradually replace parts of a legacy system with new services matches the gradual replacement approach, while others describe different strategies.

  3. Final Answer:

    To gradually replace parts of a legacy system with new services -> Option D

  4. Quick Check:

    Gradual replacement = B [OK]
Hint: Strangler fig means gradual replacement, not all at once [OK]
Common Mistakes:
  • Thinking it replaces the whole system at once
  • Confusing it with parallel running without integration
  • Assuming it merges services into one
2. Which of the following is the correct way to route requests in the Strangler fig pattern?
easy
A. Send requests randomly to either legacy or new system without control
B. Direct all requests to the legacy system until the new system is fully ready
C. Route requests step-by-step from the legacy system to new microservices
D. Stop the legacy system completely before routing any requests

Solution

  1. Step 1: Identify routing strategy in Strangler fig

    The pattern routes requests gradually from old to new components, not all at once or randomly.

  2. Step 2: Match options with routing approach

    Route requests step-by-step from the legacy system to new microservices describes step-by-step routing, which fits the pattern best.

  3. Final Answer:

    Route requests step-by-step from the legacy system to new microservices -> Option C

  4. Quick Check:

    Step-by-step routing = A [OK]
Hint: Route requests gradually, not all or random [OK]
Common Mistakes:
  • Routing all requests to legacy until full switch
  • Routing requests randomly causing inconsistency
  • Stopping legacy before new system ready
3. Consider this simplified request flow in a Strangler fig pattern: 
Legacy system handles requests for features A, B, C.
New microservice replaces feature A.
Requests for A go to new service; B and C go to legacy.
What happens when a request for feature B arrives?
medium
A. It is routed to the new microservice handling feature A
B. It is routed to the legacy system since B is not replaced yet
C. It causes an error because feature B is missing in new service
D. It is dropped and not processed

Solution

  1. Step 1: Analyze routing rules for features

    Only feature A is replaced by the new microservice; B and C remain in legacy.

  2. Step 2: Determine routing for feature B request

    Requests for B still go to legacy system as it is not replaced yet.

  3. Final Answer:

    It is routed to the legacy system since B is not replaced yet -> Option B

  4. Quick Check:

    Feature B not replaced = legacy route = C [OK]
Hint: Unreplaced features stay on legacy system [OK]
Common Mistakes:
  • Routing all requests to new service regardless of feature
  • Assuming missing features cause errors
  • Dropping requests instead of routing properly
4. A team tries to apply the Strangler fig pattern but routes all requests to the new microservice before it fully supports all features. What is the main problem with this approach?
medium
A. It leads to inconsistent behavior as new service lacks some features
B. It causes downtime because legacy system is stopped too early
C. It improves performance by forcing early migration
D. It simplifies deployment by removing legacy dependencies

Solution

  1. Step 1: Identify issue with premature routing

    Routing all requests early means new service may not handle all features yet.

  2. Step 2: Understand impact on system behavior

    This causes inconsistent or failed responses for unsupported features.

  3. Final Answer:

    It leads to inconsistent behavior as new service lacks some features -> Option A

  4. Quick Check:

    Premature routing = inconsistent behavior = A [OK]
Hint: Route only supported features to new service [OK]
Common Mistakes:
  • Thinking early routing improves performance always
  • Assuming legacy can be stopped immediately
  • Ignoring feature support gaps
5. You are designing a migration plan using the Strangler fig pattern for a large monolithic app with features X, Y, and Z. Feature X is critical and must have zero downtime. How should you apply the pattern to ensure smooth migration?
hard
A. Replace feature X first with a new microservice and route only X requests there, keep Y and Z on legacy
B. Replace all features at once to avoid partial routing complexity
C. Stop the legacy app and start new microservices for all features simultaneously
D. Keep all features on legacy until new system is fully ready, then switch all at once

Solution

  1. Step 1: Prioritize critical feature migration

    Feature X requires zero downtime, so migrate it first carefully.

  2. Step 2: Apply gradual routing for feature X only

    Route requests for X to new microservice while Y and Z remain on legacy to reduce risk.

  3. Step 3: Avoid full switch or stopping legacy abruptly

    The other options risk downtime or complexity by switching all features at once.

  4. Final Answer:

    Replace feature X first with a new microservice and route only X requests there, keep Y and Z on legacy -> Option A

  5. Quick Check:

    Gradual critical feature migration = D [OK]
Hint: Migrate critical features first, route requests gradually [OK]
Common Mistakes:
  • Trying to replace all features at once
  • Stopping legacy before new system ready
  • Delaying critical feature migration