SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b87f1e4dfa8687df26eec9959fe684a38d5305b3458a17a532e627866b0b52c' 
  AND token = 's8XK/OIqmbWxbCMNoIYmvLYEgFUlpwbaqTBSaLshwqs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00040

JSON explain

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