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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '8ab7ac4bff8d4ec9fb6ab786140fb7642736032b66b8e659cc164b32f72300b2' 
  AND token = 'Z64tYARSFltWrMTkRWRPRcuLl+DIHErJu4uswtD8oyo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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