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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6981042fb6934e9bb4da607968a4f2b1757b5c6c1f9ce82cce2d7a0df64a26a4' 
  AND token = 'QB1P6l7+WDggnomKy67wX54GfBLGmMMGjBzUEDdzPOE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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