SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b92c89d59ee3fec63d0650ff57ff1c97f14a5401df2453ffb0da1ae092102f2' 
  AND token = 'mLJltfcf3RjEPXCT8TkUzOGsDJxR5YN8hyMXyXIhAUw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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