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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '668a852e1628dfdafe0302bb583a8aa7ab67387e4b4b96896302588a992b87dd' 
  AND token = 'rcg60jujhf73we2FMHpuki7F++CYCC8DOHySqwJ6STw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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