SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '338b60b0e601623c994b60daed59f35052ab21a83b455fd436a7a79c641237de' 
  AND token = 'tjBN019QglcIng3m1LKM9avB3FEY6+sQXtXiikEYt0U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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