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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '716c20951762fee78ad86a2f7675b4d55a6efd69e1021e576f1d7053b6681404' 
  AND token = '/7mNk39MXfBzxY90wyKjW9y+aASL/t5u4KUAgSvfs2w=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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