SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '299c2a7ccc2154738cec0d5965e40f7947421ba8541d1ede5188eb579105ff2f' 
  AND token = 'rr/DZLd6zdtKYGigiSpndHS8+kvtsjKApVbjIqxsC5s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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