SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '747ca697a8a1db9efba38699e08e971882de2992ced420711cdd64a34a7e0730' 
  AND token = 'QahDGUPSoGpGXpCPjHQBg2MGNzSRab3iNTmVVZeSM88=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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