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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '9f2b114fde86e3120bd5390538305a2942e8f07d3ef63f193e481d568c922ec3' 
  AND token = '/h8xfETdKttBwogXLRPEcFCNc33/0A0reBh0x23HMgc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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