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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '18b36bd2155a26b1acf961814f21ec64c97bfb19fb924b349b92f5afd0eaa493' 
  AND token = 'C/06DBRwih1OFWTNWApXZIjxCXWMn+A1PFb5DLKR+9U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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