SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c251ffa1ce6060afa428cfdef2d9b09a86e8bffa4d7af2e0d4047104c8d33d90' 
  AND token = '+7S4i+vOE5WC2V3+88YikfDSqqzpM6ztELDF7r5BKbc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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