SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73df9e81beeb49781362699549bfb315bd51089875db1f03f2951900c85fdea3' 
  AND token = 'sd3NSJq9+yqseqnQVN08Zay18FsMFRR2SRL5BrjtAbk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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