SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5502135634915a513376418e4b86eba0f1a22c971166633a8dc31811175a9ac9' 
  AND token = 'CS73aZvVrH1aTZf6cFwxuq51XGwtVpyjBzv+j73knsg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00038

JSON explain

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