SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c21f4699851534923456ccc30d47d3dc6056ed1b6dc2ad4daf23c3f9ee701070' 
  AND token = 'OT+O1DVYRZ0ksgMDCEvPt3/dEmqVLhv8BiYVQBYrmzo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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