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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'aa52cd49b79530edd25a646a484fd6706f2a16c388cdaa6dad7a6d78a00fddd0' 
  AND token = 'az8HAPLKE+LonIy0VguE6mbeT+yNNRVvIMngyaF78cM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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