SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68abe147b7eca9afaf9a9669495790abfcea885ebc931993ba3271c6e1af9541' 
  AND token = '0YBvS+t8XD8QslblQere6E4W+qVH84AVx9nDQRc6VSE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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