SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6422490467dbc0d0c86c754a575ad953883588d8d342396d923756f765b00447' 
  AND token = 'onWTr24vsMxq+YSsz4BRPyfM220Mueg/vdUAOo1whU4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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