SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51c2a3a61f677c6d060defccc24c6169403eddd98995904886224f4480441f70' 
  AND token = 'ZJMkV1OX/8AzlBsnt2xiQyZHKQ+wk+jhfFl9dPP+ez0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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