SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8941b6bac03c14c59e6a41ba8719312ebafcc1f17a81d56a77c829449ae2534' 
  AND token = '/LGod0gBzY17lLIBipMsw0fwc1Y//umtMK7oyctgYvg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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