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SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '6b6745d1e3bb169055d34710ead74d354353c21ce1fbc8e7a50eeee2d4c90a99' 
  AND token = 'MgiZKyNQCV1CLF78SRURj/fY0oIXZrYmWfS/XS+alm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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