SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c068c5b08a968997bfa8a84bf23ba2699b47401fddbeb1c146a6b1314d7fd893' 
  AND token = 'BYvwPd+gr2mQYqC7vtBb1YRl+8HgUjyQ0GaRMu+9uCQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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