SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e4446c346ad1741605af6a0119fc0120179c68aec1d756cf40ebdde4e74541e9' 
  AND token = 'RSOXYjv0bNNaajbC+mrJsghmC3uscDGPHbVxLzyq1gY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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