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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '687661cccd5c96afffb43fa5d5bb0bed4dac44b9daab3d1fd84a1f3a5ced3dbc' 
  AND token = 'D6decY17egxynAfLhoUQs0Fv9b5tV2U8d7hG5Z2z4x0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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