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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6d8ed360d8754af19d46b867636df8f28f323ff1f58019d9a32252327e90e429' 
  AND token = 'DEdKjugbm1BTtnJieJeCPWlBsEYesDoB+YgZCapWDRg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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