SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f7e51616d402b04ac261d846af4566bc97454ed079b48ec55e6845d0c13e0676' 
  AND token = 'qOZcrWd6cdAUp9+4Nad1ctbPi4WhxdMtGqKQhix9JW4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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