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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '1fbe8d10fefd7ca4f9519f9da7d0d9a179b8a4d1b0efeb1b744ceda57e384a2c' 
  AND token = 'KhWtbPvhXZgmWatkFa7nWf1MRINhMF48t6dLtlWvXkQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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