SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35c010a2d99b85105d88e3839619348c2c9f154fb2678bec6926313a1dbfc705' 
  AND token = '/ADGa+medwtRRRSsqJP3VWB4LEeMP/JRiFM6nGt1hjk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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