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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '29dc38c44150c81050d8be0a76f678c4306529775eb3f50ec8b8b9d798402735' 
  AND token = '4x5ZaneugAKa+QGVzeQ29jNTtO1KXYs0A+tziw9389g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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