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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'ad5691ac5ee9666719bef3f53b05ca3babdc908e29e4fecba5978f271dd29f69' 
  AND token = 'sms27dCYtLQ7n9DTvcEY9d2bgycMxsNTLcjL3cnJOBM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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