Chapter 258: Scale and Tolerance

At two forty in the morning, the ticking of the monitor was magnified in the quiet ward, like a second hand slicing time apart.

Lin Chen shifted the attendant's chair back half an inch so his left leg could stretch out fully. The numbness had retreated below his ankle, replaced by a faint ache deep in the muscle. He did not rub it. He only pulled a hardbound notebook from his canvas bag and turned to a fresh page. Three columns were already ruled across the paper: time, vital signs, medication record. He checked the monitor screen and wrote: 02:40, HR 71, SpO2 97%, BP 118/76. Intracranial pressure 12 mmHg.

His handwriting was steady. The soft rasp of the pen across the paper mingled with the ticking of the machines.

From the corridor came the scrape of rubber soles against the floor. The nurse on duty pushed a treatment cart in, checked the bed card, inspected the indwelling needle, and replaced the saline bag. Her movements were practiced, with no unnecessary words.

"His temperature is coming up a little. 37.8." The nurse glanced at the digital thermometer, her tone flat. "Normal inflammatory response within forty-eight hours after surgery. Physical cooling is enough. Don't cover him up to make him sweat."

"Does he need antipyretics?" Lin Chen asked.

"Not below 38.5. Watch his urine output. If it stays under thirty milliliters for two straight hours, press the call bell." After finishing the note, the nurse pushed the cart out. The hinge turned, bringing in a trace of disinfectant from the corridor.

Lin Chen closed the notebook, got up, and went to the washroom to fill half a basin with warm water. He soaked the towel, wrung it out, and laid it across Xiaoman's forehead and the side of his neck. The water cooled quickly. Every ten minutes, he changed it. His motions were mechanical, but the rhythm was precise. He did not look at Xiaoman's face, only at the damp marks seeping from the edge of the towel and the steady waveform on the monitor.

At three fifteen, his phone screen lit up. Su Man sent a compressed file: Sandbox environment configuration checklist_v2. Mr. Zhao wants the full-chain stress-test report by ten tomorrow morning. Latency threshold capped within 200 ms.

Lin Chen opened the attachment. The checklist listed dependency library versions, database connection-pool parameters, and mock addresses for three external APIs. He scanned it once and stopped at the third line: Redis 6.2 → downgrade to 5.0 required for compatibility with the legacy serialization protocol.

He put down the towel and took his laptop from the bag. The cold light of the screen fell across his face, throwing the gray beneath his eyes into relief. The hospital corridor's Wi-Fi had only one bar, with latency jumping between 120 ms and 400 ms. He connected to his phone hotspot and opened the terminal. docker-compose up -d. The progress bar crawled upward. The fan gave off a faint hum.

The dependency download stalled while pulling the redis:5.0-alpine image. Network timeout. Retry. Timeout again.

Lin Chen did not grow irritated. He switched out of the terminal, opened the local cache directory, and found a previously downloaded redis:6.2 image. He force-renamed it with docker tag, modified the version number in docker-compose.yml to point to the local image, skipped the pull, and started the container directly.

Container started.

He ran the stress-test script. Lines of logs rolled through the terminal. P99 latency: 215ms. Timeout: 3/1000.

Over the limit. Fifteen milliseconds.

He stared at the number. The ache in his left leg suddenly sharpened, like a fine needle driving upward along the gastrocnemius. He took a deep breath, shifted all his weight onto his right leg, and typed rapidly. He adjusted the maximum idle connections in the pool, turned off the slow-query log, and changed serialization from JSON to MessagePack. Recompile. Restart service.

Run again. P99 latency: 188ms. Timeout: 0/1000.

Within target.

He saved the logs and packaged the report. The time jumped to four twenty. Outside the window, the sky was still deep black, but a faint layer of gray-blue had begun to show along the distant skyline. The air in the ward grew heavy. Xiaoman's breathing became slightly heavier, his brow faintly furrowed. Lin Chen reached out to test his forehead. The towel had already gone cool. He got up to change the water, wrung the towel dry, and laid it back in place.

At exactly five o'clock, his phone vibrated. Another bank text appeared. It was not a deposit, but a deduction notice: Your account ending in 8842 was debited RMB 4,200.00 at 05:00. Note: inpatient prepayment settlement.

The balance number shifted. He did not look at it. The thirty thousand yuan was still there; he would not touch it. The four thousand two hundred had been automatically deducted by the system, and the account was clear. He opened his bookkeeping app, entered one expense, and noted: postoperative observation period / routine settlement. Then he turned off the screen.

From the end of the corridor came the sound of a cleaner mopping the floor, the bucket knocking against the tiles. The early-shift nurses began handover. The ward door was pushed open gently, and the attending doctor came in for rounds with two residents. A stethoscope pressed against Xiaoman's chest, a pupil light swept across his eyes, and the doctor flipped through the chart.

"The peak of swelling is thirty-six to forty-eight hours after surgery," the doctor said, looking at the monitor data, his voice calm. "Intracranial pressure is stable for now. No sign of secondary bleeding. Family members should watch his level of consciousness. If you can't wake him, or if projectile vomiting occurs, notify us immediately."

"Understood." Lin Chen nodded.

The doctor turned and left. The residents followed behind, discussing medication dosage in low voices. The door closed.

Lin Chen sat back down. The pain in his left leg had become a continuous dull ache, as if it had been filled with lead. He needed to stand and move a little, but the movement had to be light. Holding the edge of the bed, he slowly straightened. His weight stayed on his right leg; the toes of his left foot only brushed the floor. Blood returning through the limb brought a burst of stinging. He clenched his back teeth and made no sound.

He walked to the window and pulled the blinds open a crack. The city was waking. Morning traffic on the distant overpass converged into a slowly moving band of light. Traffic signals changed in sequence, orderly and exact.

He returned to the laptop and opened the code editor. The stress-test report had already been generated, but the sandbox environment still needed one final full regression. He had to run the core business flow once: data ingestion, cleaning, feature extraction, model inference, result return. Every step needed timing markers.

The script reached the feature extraction module and froze. The terminal threw an error: MemoryError: Unable to allocate 2.4 GiB for an array with shape (150000, 2000) and data type float64.

Out of memory. The sandbox container had only 4G allocated, while the test dataset expanded to 6G after feature expansion.

Lin Chen stared at the error message. He did not complain about the environment limits. He opened the feature-engineering code and found the line where dimensions were expanded. The raw data contained a large number of sparse fields; direct One-Hot encoding would explode the matrix. He commented out the original logic and replaced it with HashingVectorizer for dimensionality reduction, setting n_features=2^14. A small amount of precision sacrificed in exchange for controllable memory.

Run again. The progress bar advanced steadily. Feature extraction completed. Memory usage: 2.8G.

He saved the code, committed it to the remote branch, and pushed successfully.

At six thirty, Xiaoman's fingers moved. His lips parted slightly, releasing a blurred breath of sound.

"Ge..."

Lin Chen bent over at once, keeping his voice very low. "I'm here. The surgery is done. You're in observation now. Don't move your head."

Xiaoman's eyes were half open, his pupils still a little unfocused. He seemed to want to turn his head, but Lin Chen gently held his shoulder down.

"Does it hurt?" Lin Chen asked.

Xiaoman shook his head, then closed his eyes again. His breathing gradually evened out.

Lin Chen straightened and glanced at the time. Three and a half hours until ten in the morning. The stress-test report needed Su Man's review, the sandbox environment had to stay online, the hospital payment slip had to be printed at the self-service machine on the first floor, and the painkiller for his left leg had to be taken on schedule.

He opened the drawer, found the ibuprofen prescribed by the doctor, poured water, and swallowed it. The tablet scraped down his throat with a faint bitter astringency.

His phone screen lit up. Su Man's message: Report received. Mr. Zhao moved the demo up to 9:30. Is your network stable over there?

Lin Chen replied: Stable. Connecting at 9:20.

He closed the laptop and unplugged the power. One by one, he packed the notebook, charger, medical chart folder, towel, and cup into the canvas bag. The zipper closed with a soft sound.

He went to the bedside, placed the call button within Xiaoman's reach, adjusted the height of the IV line, and confirmed the drip rate was normal. Then he turned and walked toward the door.

The moment he pushed it open, cold air from the corridor rushed at him. The early-shift nurses' station was already lit, phones ringing one after another. He supported himself against the wall and slowly made his way toward the elevator. When his left foot landed, the pain was clear and sharp. He adjusted his stride, distributing his weight between his right leg and the wall.

The elevator doors opened. It was empty inside. He stepped in and pressed 1.

The metal doors slid shut. The mirror reflected his face: hollowed eyes, blue stubble along his jaw, obvious creases at the collar of his shirt. But his gaze was very still.

He lowered his head and glanced at his phone. Nine twenty. Sandbox environment. Stress-test data. Thirty thousand in reserve. Forty-eight-hour swelling window.

All variables were within the controllable range. The error had been compressed inside tolerance.

The elevator descended. The slight sensation of weightlessness came over him. He closed his eyes and ran through the demo flow in his mind. Step one, connect the data source. Step two, trigger the cleaning pipeline. Step three, display the latency curve. Step four, answer Zhao Qiming's questions.

No unnecessary movements. No emotional fluctuations. Only steps.

Ding.

The first floor had arrived. The doors opened. Lines had already formed in the lobby for payment and medicine pickup. Disinfectant, the oily smoke from breakfast stalls, and damp morning wind mixed together.

Lin Chen walked out of the elevator, right leg first, left foot following. His pace was not fast, but it was steady.

He needed to print the settlement slip at the self-service machine first, then find a place with a stable power supply and wired network to run the sandbox environment one final time. At nine twenty, he would connect on time.

Beyond the glass doors at the end of the corridor, the sky had fully brightened. The sound of the city poured in, noisy, but orderly.

He touched the hardbound notebook in his pocket. The edges of the pages were curled now, but none of the scales inside had shifted.

The next step was connection.