SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9f7182888474d24140da2ae5d639513b0929f4fe345ce511782098d313216dae' 
  AND token = 'BQShJYl1Zm+nQZFeJnyVATM1pJv+aPEKd3wfDkGEYM8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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