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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '721701760da0246d47479d364d9f269eacfad9dc1269fd6bccece7de79b3c60d' 
  AND token = 'NCv85BSLpU9l1Dp9JlzMniyyeTfVaNLv953TKxoy+Ik=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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