SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '511b32931d5bd5f76d53365b94cb2eafeef571511398fb32da076644c6c39659' 
  AND token = 'mcMoNA+giRVOsJvuiBg2tW7PuZBTfHcXqbo8a6M/EfM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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