SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b6fc41ac998907358c342ca7711f591468963d736b52c20b038f7d2958da136' 
  AND token = 'ExzFq9ct6thtGdWRL87qIG1beY788xnREtlbrh4f/iQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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