SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '31eaea9df12624bc9cb67b1a626d39920cdeb72642f21c979219d25aa6def552' 
  AND token = 'dW83PWbDiBvcWDijWk44A0EURvXUhxEGuVbZ9Vdz22s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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