SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '347f1c3d0fa568e6519b5044160d3eecc78a865da74e1d6421bb5d6c17256438' 
  AND token = 'BkYLsrJDYwE/Um+QX0m2GPxOEpYX4ueJiaoZcJKrvn0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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