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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c7ab4ad58ea10be8573017eaad8def760b703a2ed9409e8a7e3e1f70624a3e33' 
  AND token = 'dDhuAywwf3YuKpxRekmqvQNdNZKaAORBpRz6ZXBbBV8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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