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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c7f4a20849768039033449224bf550b041339b96eca435fd7aee566e81efb030' 
  AND token = '5Bmx7Fobm8TKiB1YrHL2HdWHigwwFotBrrVoSY1DrDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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