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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0f68da1e402b78f0e99994b90cdb241bf771ec9dadceca72b36eeeaf2fe9d472' 
  AND token = 'HPU7nMzM5r0EVb3kBWuHeG6sZ4JFnGCHSsf3AdfCUgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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