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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5f81e9b6a4cbffb1393bd92e112fc7fe7ab1b5d2d27da9bd47a534c76b07a245' 
  AND token = 'MfPz5xXBMnZbSQmnRnPghjlyShehYCuBDQbA+0nWYZY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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