SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5cb76843002012d52989a25d9b1459ae5a3c16b79e343a4fd271ff50f6336326' 
  AND token = 'QYLVdQiM8odWeJ2CUfVKzDwieRgt/PFJxqdrKqFe1uU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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