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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '7b6b441e6a09db0372e7bd3871cdcdba095d5e37018a956405353d3bcc8c3608' 
  AND token = 'LQARx5Zmy1N9JxmAJbIVhUTCb4CGic7v87H//37vJhI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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