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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b8b0bc4b12bb2026b174dfbb8a849699a482f8b048397adadec992a4424d64f8' 
  AND token = 'pmGpTD7yd3+jz7GRcnTXk4pp1uvOk8nDfRbmfz6OCF4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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