SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b46b353f17e32012fad5d9037d29e94c3986bf613fa050cb6add86d3cf717b2' 
  AND token = '6zqjHTTcHSNiX9cH/PVNyFqGo3dEHZkzVqvMlT0oPTs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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