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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '78bd7135dff1a14f32d4b76550f93df80150c73ee4ba47680bc2fbdbd09ac6d4' 
  AND token = '0RYPSc+DX7iV7KHStFkz9nRdUdDnKyEntQzcF/9YMpA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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