SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '168ec9b834ff22f36144fad9ec99fd931b60e1245e433cd64dd0a08237e1dbd2' 
  AND token = 'fZUJcDEgW66wFp79PTfML2H33zCtu8GliMpzes8LKEk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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