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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c253bed7a371cc2ae8b72e4a428ff973b2fc8dcde5bed47e669d1072255144dd' 
  AND token = 'ERbG3ta0ljahIZJjgY16fG8VW3zNmW5ER+Qv+jfNMJ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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