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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'e7e4e956251a225ff440716bb0a3ef0b21c1362891a3e7faba52383511605994' 
  AND token = 'zngV7apQMS+dWTuT5eEwmdb/StfdXb1K9cLTqtvJMgg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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