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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1f3de397fcfba54318673c091be45f25064948eba59880d5ba22475982f710c3' 
  AND token = 'd8gxFcIiap7tUaNC9eydjijV6bNSx1cX/GzdVKx1n2E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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