SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ad8bddaded735db832a8a361b5f3644d45b6e9f5470242392ce6ad76efa5d8c' 
  AND token = 'gJICV51DE7KwKh0T5EEFMDrIplqMs90aLF3vuuPpgfU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}