SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42b8623abf329da2ea95338187b2ff1fe5de90c3314c0fde34ab05238fb8ad03' 
  AND token = 'nyQK64uHLhgLAmwcS5eK80GTIq68kPpVXYRoOwY3sYU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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