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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6eb11b6fed184828f790590900b15d3cf6b4d020dd6f2b785a95b8c0ded30e7e' 
  AND token = 'N0/Xcnew9G6v0EL7wVGyrZOIOfaI/b3wHCpUeInf+wE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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