SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b344e04c73d7f1a1811950185c00eacd4436c478af8ca5fe57a2fa6da1062210' 
  AND token = 'aMWlWFRVG6cdLSgAkKcnthFcwhQ/4TE292ca0tmxVRc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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