SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8e888e563f27adf9c8c639063566a544bbe123315019f49302fcfcec2f78305' 
  AND token = 'vKwKc9CKj+rRA4fB0D6GUsNBqiqKXqoP5xg/oI//3Lw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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