SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21cc5e7e94e5dcba0c4a847907756f53426be5017d5d0f30089c18692198d5ed' 
  AND token = 'UK4hXKWScgu27BBsTWwpXnASvQjTJiDKfQ1aJ/+hwkw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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