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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'dcd3b44bf4d0a965e334987a23751a5df7a6494a73f4c65056bc607a279f5d56' 
  AND token = 'fqPbmJHI/KSgScS1mSGRvRxsSD/x37pHAcgV+U3zNkc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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