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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'cd0c8eeaa9e80acae1f3216cabf57e5c9bf8f7f11a3c4b909db12ff7dd240f52' 
  AND token = '/vX7cW4ZT+EyY2lwLvQKvO/e3fThva+S0zCuv3VhIiQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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