SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '856d457abea029cd43cbdfcea7ac166d4204b29f2127320eba0325a3b7b638cb' 
  AND token = '/DBi2hDFc19WSPdwTmUion0a2dmFyluRei5zZ4YrCdg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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