SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3291e2643249ad91259dac74e8dae742985caa36a3a12d293f55d3c7517c55bb' 
  AND token = 'iNvU08LjErhs5LqifI0TLqQ9+X3tmkZx86kKMMYPyMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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