SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c204808226942afe2b848e8294520b8d00d569e969b736a39efb047c1330ca03' 
  AND token = 'WSWvGZ4cUGtxXfFymz1zymIodVkDxuqDEUwFYFSTNys=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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