SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68d4db810376a1a6426d91bc234e4a3d450b5903504f073f3166e0743f2e7928' 
  AND token = '9bT+qPQFm3UM+Y4zZlLIsVKdLJzQJR8vudirlpvN55I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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