SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b84f79ec93398414bfcb6733a310645dd470dde4e7c47b2691896d4872270666' 
  AND token = '6Q3LJzLOdRrrF4b2UEmiEsOv4FRrEPxXfbawnwBADMM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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