SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f848450e463650df24aec45e20621b5a65e5612612a6cb8670c81df03988b252' 
  AND token = 'onDsw8fJkcfZnbyFwkc2QP3WZl+yQ+uisKkRX+Kjxu4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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