SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8eb60ec690a31d0c299274dd60c55fbed568f3ce80af655ef984d8cee962e43' 
  AND token = 'KD3xlfqOhDihYJFJ4MuLIOQVEwScggB/DbPuajsof6s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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