SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3feb4f952a60bde4037ad04065903aa913e94cd06e8ba7875a71c19d068cda74' 
  AND token = 'QAyuPUwqlegnUmwRaHLP3YXdcZcMnUqxFLfyoiBpW8I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}