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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '0f51451949a3770f42f18dbc903dde094d7381ace4636b089cd8fb0b56c59c79' 
  AND token = 'tC5QeBo/9mUkK5hwPTCrC0PPAOh4bSF7gWUbOMiuW+g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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