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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f21cadfe1b03dfbb6861c197262d8e60c16a4d47da2346c5eb82b5021e376f71' 
  AND token = 'mdkvSe5HXrBV85cvogBNrZkAf09QRpj4s4knyqE3C4k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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