SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd4a1357c2c27b735ed937a63013ef6858ec6a7d92deb95b7deac0075a551acde' 
  AND token = 'dxf636TZcXLwXtty57k9sqWwEkRZ1RORg2hQJYBpnP4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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