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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'da31574eaa6bd804a31f5cadb11c7d8f0d5fa5dd9655028dc2df764a1aada881' 
  AND token = 'SUPvyUgQ2JN5rpeVUWhdX2FuSE2HaY8c93F9rVN0Yzg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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