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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a76400ed70d3d72dd3663402665fa6772e8ca2548024947b25a4fde49e0c5b50' 
  AND token = 'IY4MYxCZJjSgvRD8gaS8Yn8TBcFMSICFgF2tlWIZa5Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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