SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3ce6e5c20f8bd504d1a694373a0d554160756210979a11d408788776a562f37b' 
  AND token = 'N/GUnczQaiT8R/r8tvcYfd8TL0o/UWiDxMGO9ONah4g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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