SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31e54655a1e8d0bc09875c938322cd8e273646aa09cf943621a41ee1b06df839' 
  AND token = '2h371lt5r/1qVPI/aTxBOMYkTBFHpiN3++8N2+aBGzU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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