SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4b504d2427a343e22c2fc736aea3a956d833062c99198d7e9436da0468f3c5f9' 
  AND token = '4p62LuyLum0bdPnuAHRB0XGSOoQx5uVILynpSHcRFmM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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