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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b6696f8d96b3a4c1fe0d2b654432228731929b96c59abdfd8a6207f0414234af' 
  AND token = '0BDYF43aQ7vVXvMe4viwDS4vc5KNNdzSmk6dfvokedM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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