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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c891d72cfef702c97781ddf0a019b6dcdc169b6f114ef343121d073071e09909' 
  AND token = 'QqGXnb5KwMwUxpay5LfErLj8NjKLOUSuh5FW86nbcL4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00044

JSON explain

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