SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39bcaf6fa934e9d7db973eb0b69df693db647a64edc7aca03a103c58dd4efe09' 
  AND token = 'TeufbscnDNSHHDBLX1h1rQkC7crtKkYRkyElK48Fpps=' 
  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"
    }
  }
}