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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '79cff46c1a8b30e83c28eb0bea8ce7a9ce29046fe6aa72e9da6023da6ba043f7' 
  AND token = '8nN4yO0ZkQEOkHlJrLxKTZlKPE3DxF/5L0/VPghRPP0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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