SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8f0eaa20f02f9168de3cc492e8ce0a292046855d17a59d897307023289208d3' 
  AND token = 'MRqYSd5Zx50KIbJDJjPsdrVE1xIRbKJcnG4UbpcHYE8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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