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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb78f7fcbdaa701dad95fce2a214a05ac9668bfb25c59f357f7f8edcda789ece' 
  AND token = '81SYC4D93phfeE8I2kW4SQq9EA6+Tu2VIUtMTxmVQvU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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