Feature vectors for serving

In Part 1, the Entity class already defined get_feature_vector(), so you do not need to jump back and edit earlier cells here. This page focuses on how that method works in serving and how to validate its behavior.

Use get_feature_vector

Unlike the other Entity methods that use the Spark connector for batch reads, get_feature_vector uses the Aerospike Python client. It accepts the as_client connection you created on the previous page.

get_feature_vector looks up one record by primary key and calls as_client.select(...) to return only the bins in feature_list.

1. Run Cell 19 to retrieve one driver’s feature vector.

Cell 19: Retrieve one driver’s feature vector

feature_columns = ["ds_decl_rate", "ds_avg_rating", "da_trips_today"]

features = Entity.get_feature_vector(as_client, "driver", "driver_042", feature_columns)
print(f"Features for driver_042: {features}")

Expected output

Features for driver_042: {'ds_decl_rate': 0.061, 'ds_avg_rating': 4.72, 'da_trips_today': 11}

• as_client: Aerospike Python client connection
• etype: entity type (for example, "driver")
• eid: entity ID (for example, "driver_042")
• feature_list: bins to retrieve (for example, ["ds_decl_rate", "ds_avg_rating", "da_trips_today"])
• Returns {feature_name: value}, or None if the entity doesn’t exist

Test with known drivers

Try a few drivers to see the range of feature values. Recall from Part 2 that drivers with ds_decl_rate >= 0.10 were labeled as higher decline risk.

1. Run Cell 20 to retrieve feature vectors for test drivers.

Cell 20: Retrieve feature vectors for test drivers

feature_columns = ["ds_decl_rate", "ds_avg_rating", "da_trips_today"]
test_drivers = ["driver_005", "driver_042", "driver_087"]

for driver_id in test_drivers:
    fv = Entity.get_feature_vector(as_client, "driver", driver_id, feature_columns)
    if fv is None:
        print(f"{driver_id}: not found")
        continue
    risk = "higher" if fv["ds_decl_rate"] >= 0.10 else "typical"
    print(f"{driver_id}: decline_rate={fv['ds_decl_rate']:.3f}, "
          f"rating={fv['ds_avg_rating']:.2f}, "
          f"trips_today={fv['da_trips_today']}  ({risk} risk)")

Expected output

driver_005: decline_rate=0.048, rating=4.81, trips_today=3  (typical risk)
driver_042: decline_rate=0.061, rating=4.72, trips_today=11  (typical risk)
driver_087: decline_rate=0.167, rating=4.22, trips_today=9  (higher risk)

Your values will differ, but you should see a mix of typical and higher-risk drivers based on the threshold.

Measure retrieval time

Run 100 individual lookups (one per driver) to get a stable latency measurement. Each lookup retrieves the same 3-feature vector for one driver.

1. Run Cell 21 to benchmark 100 feature vector retrievals.

Cell 21: Benchmark 100 feature vector retrievals

import time

feature_columns = ["ds_decl_rate", "ds_avg_rating", "da_trips_today"]
timings = []

for i in range(1, 101):
    driver_id = f"driver_{i:03d}"
    start = time.perf_counter()
    Entity.get_feature_vector(as_client, "driver", driver_id, feature_columns)
    elapsed = (time.perf_counter() - start) * 1000
    timings.append(elapsed)

timings.sort()
print("Feature retrieval benchmark: 100 lookups (3 features each)")
print(f"  p50: {timings[49]:.2f} ms")
print(f"  p95: {timings[94]:.2f} ms")
print(f"  p99: {timings[98]:.2f} ms")

Expected output

Feature retrieval benchmark: 100 lookups (3 features each)
  p50: 0.22 ms
  p95: 0.38 ms
  p99: 0.45 ms

Retrieval stays sub-millisecond across the sample. Each call is a single key lookup, and Aerospike returns the requested bins directly.

You now have a fast feature retrieval method. Next, you’ll connect it to the trained model to make predictions.

Checklist

• I understand how get_feature_vector() performs low-latency feature reads.
• I can retrieve a driver’s features by ID in under a millisecond.