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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b75cc6b9015fa0f2e08d75a4eeb547fe448a4a67a107d92de0b84eceb018f6b4' 
  AND token = 'qdy2eT1QXWDxgbk3CWC+9Dif6e6A2S0TqQZcClXpcYE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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