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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e3e5601eff58fcfdeebe69063de197a5f7d9ec19910257cde119ffaa5ed837a3' 
  AND token = 't3PXxcGMBGGi8/ilLvsMxBl0cvkqrL2V9nbt5MURlhQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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