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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'beef6173efa18a252f31581855c7f4e97fbd509e54afc8ce033e30fcdf00c2c2' 
  AND token = 'P0JFfSUjUfmA5kEwAJtxVxsk4+NuqUm/0EOtCtc4/5Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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