SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68612b6c07af8a004453c49f7cdb5179e7f15a74a91c3715a8d0e73f10e0fcb9' 
  AND token = '99QLLfJwoFVB+WEG4eF7Pv/PeGZhvAVguXPWSuzf5F8=' 
  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"
    }
  }
}