SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42fddf72a70bdd83392dda0716c510ae87a54ded9885e377249b14f6e1ff9a64' 
  AND token = 'fBdt6+jFqaPY9xYp6xVUmbGidhWKmVYmLcogvejfheQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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