SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b76dd934479ddf1164d1c2a7346ec3bea7a7f7f0ebc617da7f0913c8dc8d4171' 
  AND token = 'IvTvSC9JP5bs4CZyHwBrKLpPqg/vsYKQ/tdIzu/5T90=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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