SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5ad36dd99b2c20387564b6800003d077d647bf4d43e4676cbf0f1b3cee9e066f' 
  AND token = '5lfGchH48yADMx8RuJUElo+w5R4mMaMoow0pNsrTJnY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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