SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75a33ad72054480d364bccc88aaab197e7b6993b4c18067ff5f268d47256d42d' 
  AND token = '5BgP5iVwwQjfJTHoL5cL8P/2K+7dwsoiAdLU2eFGQxk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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