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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '42c297ebd09aa17af72db15ff99ed9dc123bc84b43b11f46372d8a3806721728' 
  AND token = 'xb3SiAHoco7rjj5MGyP1lmWT125VBar6xlzkveEPRNw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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