SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8dfa0532994e257f846790eb0feab825f7290597d0f475d9f3b15fa42122d5c4' 
  AND token = 'TQiKqcbvHidh6/TaeegygVkp/mGyFkBrOslWQPBlbjM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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