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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '76db600f59b73b8e9ba125ae1cc4d9283af13612efca03572df8338dda0d608e' 
  AND token = 'S+HyqKntWqHZH5/3LfDhTUGDAcfbqLw2pmatqzyDeMg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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