SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21c84ab9dbde959599c8b535e9b3aff66bbab680d4370a433c862a314246932f' 
  AND token = 'J3z7HkeliGLEy3V7CfuPZ3goWBsxLV6ayD8m+/2+HzQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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