SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6fdd5223683fca878826d31fc5d097db870c7b1aa9667a2d0d4ef90d98691d4f' 
  AND token = 'sFQJ7Uulzwg5jKeE3qUZOGoRyl6qIbchdBjVd5M1zwA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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