SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6e31ec66f164bfc50a23c3fd79d7d1e84f63ead7b57fd8f5aa95995f842bda78' 
  AND token = 'OJmVjBn/ZiVegbQK+UgnUs9dsJr7BRSgUROl98jCsHI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}