SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5de043db2bb5b919e76e8be4f1c2e656add3a7cfec54143bd262c1dfb6635633' 
  AND token = 'k/DNArpZsSjy8sHt1LtfCKSjDAnYyIFb2yLFUwS3kQ8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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