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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'dc378df798b08abcc653a24d5439d00d9bf9d9eb83cccb6f1f66bb8a4af0665c' 
  AND token = 'dfTY3z37KpxAlH3YMaG0RxcWwTMyH9gtRCO9sMYpI/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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