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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9521e8b9f92608e1202b3d6f7d31a5f8446ba759db66e7a2a41beea68f49a400' 
  AND token = 'WFd5YfzjYMJ0nOQdjNnYeWSvKFdSRo5VwD/KeU0W+HM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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