SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6ddaf6a067ce925b647b280921c5bf72063db69a1602d745e80491a7bee5d9d' 
  AND token = 'O8g/02gMdVjQdFaTcvbEyec1Nf0rJgbBqramnALvN4I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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