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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e6ce8ef0f34072555da6babf096816692a912b0f0cb862c1de84c59961f422da' 
  AND token = 'UZ2AiqVSD8V8wmHiBRGkUn56GfaTf+n8fUspfn23LC0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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