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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '273a2cdcaa311f9f818dbc05a0ff2fb349d1310fe599ed0da15d6508f14d5778' 
  AND token = 'da9LcQ7s9FbeySY9lTj4AJtb6A9jGNerk5f/2euh8q4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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