SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b691f5f784d51fa84ce4796c1aa89353edbe1eed8e7d939333eddb20397a78b4' 
  AND token = 'Nvl+kemOuXY/sxTi57wqpEXj6HpQq9duFsqSLxPgA00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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